Hi!
8.5oz is a lot of dead weight...let's see that's around 250g...wow!!
Get rid of it as fast as you can! And move all servos and batteries /receiver as far forward as possible.
A .76 engine in a .40 trainer????
No way! Way too much engine!

Gaps are not good! Just use a strip of plastic filmcovering (Oracover) an iron it down over the gap. See picture of my aileron on my Q-500 racer.


Regards!
Jan K
Sweden