RE: What does you Funtana 90 weigh?
Your weight and balance issue is just wild...I was able to balance a Super Tigre G-90 set-up by mounting a 1200 mA/h battery on a post next to the engine.
Interestingly enough...I didn't even have a chance to test-fly it before getting my hands on a SWEET Saito 150. The plane is on the Diningroom table as we speak (err, type) I'm having a heck of a time figuring out how to mount it far enough beck. The mounts I have won't let the motor slide back far enough.
Hmmm
Anyway, You've given me more inspiration!
Here's a pic that inspired the battery location idea...
Keep us posted. I'm really curious as to the longevity of our planes with twice the recommended power.