I am thinking the weight might be less than anticipated.

With two 1100-mAh NiCd's and the IBEC you will be able to do 7-8 full flights with a good safety margin. Power consumption will be approximately 150-200 mAh per flight for both servos and ignition.

This makes it easier since you won't have to use a voltage regulator for the Rx.

Also, you will need only a 11 or 12 oz fuel tank, and you could get away with a much smaller tank if you limit it to 8-minute flights.

A lot of guys are flying this engine in 3D models such as the Extreme Flight Extra, 78-inch wingspan, and some other 3D models. some weighing over 12 lbs. However, they are using a Vess prop, either an 18x6 or a special 18.5x15.5 version, both developing more than 20 lbs of thrust. Noisy as hell but pulls like a beast.