diff --git a/src/statebag/boardstate.py b/src/statebag/boardstate.py
--- a/src/statebag/boardstate.py
+++ b/src/statebag/boardstate.py
@@ -1,14 +1,23 @@
 from util import EMPTY,BLACK,WHITE, hashBoard,exportBoard
-from go.engine import getTransitionSequence
+from go.engine import getTransitionSequence,SpecGo
+
+
+g=SpecGo()
 
 
 ## Crude lower bound on edit distance between states.
-def estimateDistance(diff):
+def estimateDistance(diff,s1,s2):
 	# lot of room for improvements
-	additions=sum(1 for d in diff if d[2]=="+")
-	deletions=sum(1 for d in diff if d[2]=="-")
-	replacements=len(diff)-additions-deletions
-	if additions>0: return additions+replacements
+	additions=deletions=replacements=unaccounted=0
+	for (r,c,d,color) in diff:
+		if d=="+": additions+=1
+		elif d=="-":
+			deletions+=1
+			for (ri,ci) in g.listNeighbours(r,c):
+				if s1[ri][ci]==EMPTY and s2[ri][ci]==EMPTY:
+					unaccounted+=1
+		else: replacements+=1
+	if additions>0 or unaccounted>0: return additions+replacements+unaccounted
 	elif replacements==0 and deletions>0: return 2 # take n, return 1
 	return replacements+1 # ???
 
@@ -53,8 +62,10 @@ class BoardState:
 		self._hash=None
 
 	def tryConnect(self,s,diff=None):
+		""":param s: BoardState s
+		:param diff: [(r,c,change,color), ...], change in {+,-,*}, color in {BLACK,WHITE}"""
 		if diff is None: diff=self-s
-		distEst=estimateDistance(diff)
+		distEst=estimateDistance(diff,s,self)
 		if distEst>3: return # we couldn't find every such move sequence anyway without a clever algorithm
 		weightEst=s.getWeight()+2-distEst
 		if weightEst<=self.getWeight(): return