diff --git a/lib/bcoin/bst.js b/lib/bcoin/bst.js
index b8fb524d..f60aa50f 100644
--- a/lib/bcoin/bst.js
+++ b/lib/bcoin/bst.js
@@ -680,11 +680,6 @@ Iterator.prototype.seek = function seek(key) {
   this.index = utils.binarySearch(this.items, key, function(a, b) {
     return self.tree.compare(a.key, b);
   }, true);
-
-  item = this.items[this.index];
-
-  if (!item || this.tree.compare(item.key, key) !== 0)
-    this.index += 1;
 };
 
 Iterator.prototype._end = function end() {
diff --git a/lib/bcoin/fees.js b/lib/bcoin/fees.js
index 1f5f3781..04e42e1d 100644
--- a/lib/bcoin/fees.js
+++ b/lib/bcoin/fees.js
@@ -9,6 +9,8 @@
 'use strict';
 
 var bcoin = require('./env');
+var utils = bcoin.utils;
+var assert = require('assert');
 var constants = bcoin.protocol.constants;
 var global = bcoin.utils.global;
 var Float64Array = global.Float64Array || Array;
@@ -55,11 +57,11 @@ function ConfirmStats(buckets, maxConfirms, decay, type) {
   this.type = type;
 
   this.buckets = new Float64Array(buckets.length);
-  this.bucketMap = {};
+  this.bucketMap = new DoubleMap();
 
   for (i = 0; i < buckets.length; i++) {
     this.buckets[i] = buckets[i];
-    this.bucketMap[buckets[i]] = i;
+    this.bucketMap.insert(buckets[i], i);
   }
 
   this.confAvg = new Array(maxConfirms);
@@ -109,7 +111,7 @@ ConfirmStats.prototype.record = function record(blocks, val) {
   if (blocks < 1)
     return;
 
-  bucketIndex = this.bucketMap[val];
+  bucketIndex = this.bucketMap.search(val);
 
   for (i = blocks; i <= this.curBlockConf.length; i++)
     this.curBlockConf[i - 1][bucketIndex]++;
@@ -210,9 +212,10 @@ ConfirmStats.prototype.estimateMedian = function estimateMedian(target, needed,
     }
   }
 
-  // bcoin.debug('estimatefee: target=%d.'
-  //   + ' For conf success %s %d need %s %s: %d from buckets %d - %d.'
-  //   + ' Cur Bucket stats %d% %d/%d (%d mempool).',
+  // bcoin.debug('estimatefee: '
+  //   + ' For confirmation success in %d blocks'
+  //   + ' %s %d need %s %s: %d from buckets %d - %d.'
+  //   + ' Current bucket stats %d% %d/%d (%d mempool).',
   //   target,
   //   greater ? '>' : '<',
   //   breakpoint,
@@ -237,10 +240,10 @@ ConfirmStats.prototype.estimateMedian = function estimateMedian(target, needed,
  */
 
 ConfirmStats.prototype.addTX = function addTX(height, val) {
-  var bucketIndex = this.bucketMap[val];
+  var bucketIndex = this.bucketMap.search(val);
   var blockIndex = height % this.unconfTX.length;
   this.unconfTX[blockIndex][bucketIndex]++;
-  bcoin.debug('estimatefee: Adding TX to %s.', this.type);
+  bcoin.debug('estimatefee: Adding tx to %s.', this.type);
   return bucketIndex;
 };
 
@@ -268,7 +271,7 @@ ConfirmStats.prototype.removeTX = function removeTX(entryHeight, bestHeight, buc
       this.oldUnconfTX[bucketIndex]--;
     } else {
       bcoin.debug('estimatefee:'
-        + ' Mempool tx removed from >25 blocks,bucketIndex=%d already.',
+        + ' Mempool tx removed >25 blocks (bucket=%d).',
         bucketIndex);
     }
   } else {
@@ -277,7 +280,7 @@ ConfirmStats.prototype.removeTX = function removeTX(entryHeight, bestHeight, buc
       this.unconfTX[blockIndex][bucketIndex]--;
     } else {
       bcoin.debug('estimatefee:'
-       + ' Mempool tx removed from blockIndex=%d,bucketIndex=%d already.',
+       + ' Mempool tx removed (block=%d, bucket=%d).',
        blockIndex, bucketIndex);
     }
   }
@@ -352,7 +355,7 @@ PolicyEstimator.prototype.removeTX = function removeTX(hash) {
   var item = this.map[hash];
 
   if (!item) {
-    bcoin.debug('estimatefee: mempool tx %s not found.', hash);
+    bcoin.debug('estimatefee: Mempool tx %s not found.', hash);
     return;
   }
 
@@ -437,7 +440,7 @@ PolicyEstimator.prototype.processTX = function processTX(entry, current) {
     };
     bcoin.debug('estimatefee: Rate: %d.', this.estimateFee());
   } else {
-    bcoin.debug('estimatefee: Not adding ts %s.', hash);
+    bcoin.debug('estimatefee: Not adding tx %s.', hash);
   }
 
 };
@@ -457,7 +460,11 @@ PolicyEstimator.prototype.processBlockTX = function processBlockTX(height, entry
 
   blocks = height - entry.height;
   if (blocks <= 0) {
-    bcoin.debug('estimatefee: TX had negative blocks to confirm.');
+    bcoin.debug(
+      'estimatefee: Block tx %s had negative blocks to confirm (%d, %d).',
+      entry.tx.hash('hex'),
+      height,
+      entry.height);
     return;
   }
 
@@ -632,6 +639,37 @@ PolicyEstimator.prototype.estimatePriority = function estimatePriority(target, s
   return priority;
 };
 
+/**
+ * DoubleMap
+ * @private
+ */
+
+function DoubleMap() {
+  if (!(this instanceof DoubleMap))
+    return new DoubleMap();
+
+  this.buckets = [];
+}
+
+DoubleMap.prototype.insert = function insert(key, value) {
+  var i = utils.binarySearch(this.buckets, key, compare, true);
+  this.buckets.splice(i, 0, [key, value]);
+};
+
+DoubleMap.prototype.search = function search(key) {
+  var i = utils.binarySearch(this.buckets, key, compare, true);
+  assert(this.buckets.length !== 0, 'Cannot search.');
+  return this.buckets[i][1];
+};
+
+/*
+ * Helpers
+ */
+
+function compare(a, b) {
+  return a[0] - b;
+}
+
 /*
  * Expose
  */
diff --git a/lib/bcoin/http/server.js b/lib/bcoin/http/server.js
index dc7013e7..eaf9977b 100644
--- a/lib/bcoin/http/server.js
+++ b/lib/bcoin/http/server.js
@@ -414,12 +414,8 @@ HTTPServer.prototype._init = function _init() {
   this.post('/wallet/:id/send', function(req, res, next, send) {
     var id = req.options.id;
     var options = req.options;
-    var outputs = req.options.outputs;
 
-    if (!Array.isArray(outputs))
-      return send(400);
-
-    self.walletdb.createTX(id, options, outputs, function(err, tx) {
+    self.walletdb.createTX(id, options, function(err, tx) {
       if (err)
         return next(err);
 
diff --git a/lib/bcoin/mempool.js b/lib/bcoin/mempool.js
index 1c0f102f..a1dd5d72 100644
--- a/lib/bcoin/mempool.js
+++ b/lib/bcoin/mempool.js
@@ -727,8 +727,12 @@ Mempool.prototype.addTX = function addTX(tx, callback, force) {
   }
 
   if (this.requireStandard) {
-    if (!tx.isStandard(flags, ret))
-      return callback(new VerifyError(tx, ret.reason, 0));
+    if (!tx.isStandard(flags, ret)) {
+      return callback(new VerifyError(tx,
+        'nonstandard',
+        ret.reason,
+        0));
+    }
 
     if (!this.chain.csvActive && tx.version >= 2) {
       return callback(new VerifyError(tx,
diff --git a/lib/bcoin/tx.js b/lib/bcoin/tx.js
index 65d2eb36..c70a0e64 100644
--- a/lib/bcoin/tx.js
+++ b/lib/bcoin/tx.js
@@ -1371,7 +1371,7 @@ TX.prototype.checkInputs = function checkInputs(spendHeight, ret) {
     input = this.inputs[i];
     coin = input.coin;
 
-    if (coin.coinbase) {
+    if (coin.coinbase && spendHeight != null) {
       if (spendHeight - coin.height < constants.tx.COINBASE_MATURITY) {
         ret.reason = 'bad-txns-premature-spend-of-coinbase';
         ret.score = 0;
diff --git a/lib/bcoin/utils.js b/lib/bcoin/utils.js
index 1f89ed17..2bff8188 100644
--- a/lib/bcoin/utils.js
+++ b/lib/bcoin/utils.js
@@ -2415,7 +2415,7 @@ utils.binarySearch = function binarySearch(items, key, compare, insert) {
   if (!insert)
     return -1;
 
-  return start - 1;
+  return start;
 };
 
 /**
@@ -2428,7 +2428,7 @@ utils.binarySearch = function binarySearch(items, key, compare, insert) {
 
 utils.binaryInsert = function binaryInsert(items, item, compare) {
   var i = utils.binarySearch(items, item, compare, true);
-  items.splice(i + 1, 0, item);
+  items.splice(i, 0, item);
   return items.length;
 };
 
diff --git a/lib/bcoin/wallet.js b/lib/bcoin/wallet.js
index 06a3de22..6d53ad41 100644
--- a/lib/bcoin/wallet.js
+++ b/lib/bcoin/wallet.js
@@ -592,34 +592,21 @@ Wallet.prototype.fill = function fill(tx, options, callback) {
  * sort the members according to BIP69, set locktime,
  * and sign it (accesses db).
  * @param {Object} options - See {@link Wallet#fill options}.
- * @param {Object[]} outputs - See {@link Script.createOutputScript}.
+ * @param {Object[]} options.outputs - See {@link Script.createOutputScript}.
  * @param {Function} callback - Returns [Error, {@link MTX}].
  */
 
-Wallet.prototype.createTX = function createTX(options, outputs, callback) {
+Wallet.prototype.createTX = function createTX(options, callback) {
   var self = this;
-  var height = 0xffffffff;
-  var tx, i;
-
-  if (typeof outputs === 'function') {
-    callback = outputs;
-    outputs = null;
-  }
-
-  if (!outputs) {
-    outputs = options;
-    options = {};
-  }
-
-  if (!Array.isArray(outputs))
-    outputs = [outputs];
-
-  if (options.height >= 0)
-    height = options.height;
+  var outputs = options.outputs || [];
+  var i, tx;
 
   // Create mutable tx
   tx = bcoin.mtx();
 
+  if (outputs.length === 0)
+    outputs.push(options);
+
   // Add the outputs
   for (i = 0; i < outputs.length; i++) {
     try {
@@ -648,7 +635,7 @@ Wallet.prototype.createTX = function createTX(options, outputs, callback) {
     if (!tx.isSane())
       return callback(new Error('CheckTransaction failed.'));
 
-    if (!tx.checkInputs(height))
+    if (!tx.checkInputs(options.height))
       return callback(new Error('CheckInputs failed.'));
 
     self.scriptInputs(tx, function(err, total) {