I have a hard time with the bubble type balancers. I use one from Dubro now and it works very well, very sensitive, and I have had as large as 34x14 2 blade and a 32x12 3 blade on it. Balances 3 blades as well as it does 2 blades.
http://www3.towerhobbies.com/cgi-bin...&I=LXD712&P=ML