I and several friends use this one; http://www.rcuniverse.com/forum/m_708060/tm.htm
have used it to balance a Don Smith Cionnie, Comp ARF Mustang, Ziroli Stuka & Zero. 1/4 scale P-39, 1/5 Mustang, 1/6 T-6, 1/3 Pup, and many others. Works really well, and if you use a pulley at the top, you can do heavy models by yourself.