reduce safety margin to 2%

lib/model/txproposal.js

@@ -239,7 +239,7 @@ TxProposal.prototype.getEstimatedSizeForSingleInput = function() {
 
 TxProposal.prototype.getEstimatedSize = function() {
   // Note: found empirically based on all multisig P2SH inputs and within m & n allowed limits.
-  var safetyMargin = 0.05;
+  var safetyMargin = 0.02;
 
   var overhead = 4 + 4 + 9 + 9;
   var inputSize = this.getEstimatedSizeForSingleInput();

test/models/txproposal.js

@@ -56,7 +56,7 @@ describe('TxProposal', function() {
   describe('#getEstimatedSize', function() {
     it('should return estimated size in bytes', function() {
       var x = TxProposal.fromObj(aTXP());
-      x.getEstimatedSize().should.equal(407);
+      x.getEstimatedSize().should.equal(396);
     });
   });