stuff the battery up under the tank. At 3 inches the plane will be quite twitchy.

What engine are you using. I have seen the 60 with a Saito 100 need 6oz and according to the builder it flew very well.

Here is where that discussion starts

http://www.rcuniverse.com/forum/fb.asp?m=3264351

At first he thought he had 12oz but it ended up being 6oz