I am currently flying a twister with a Super Tigre G90 and its awesome, ballistic vertical and it ballances right in the middle of the recomended range with the receiver and battery as far back as you can get them. If you are worried about the exta weight of the engine you just need to compensate in other areas, I run a timber prop (14x6) mini servo on throttle a light receiver (eg hitec electron 6) and made up my own 6v AAA receiver pack.Hope this helps.

Cheers

Weedy