Do a search on google or the GLiders and Sailplane forum here at RCU for "dive test".

The sailplane guys use this test for setting their balance point close to neutral. The same test can also work for your funfly. Set the engine power to about 1/4 revs and trim the elevator so the model is happy flying hands off in level flight then do the test.

Set your balance and retrim the elevator until the model either does not try to tuck or pull out or just trys to pull out very slowly. That's where you want it to be for a fun fly. It'll fly like it's balanced on a tightrope at that point but you'll have LOTS of elevator authourity. If you find it wanders in pitch move the balance forward very slightly to regain some small amount of pitch stability. Not too much though or you'll be back where you are starting.