Awesome scheme.

Personally, I run two 7.4V 2100mah Lipos on my 33%. I don't run a regulator. The 170's and 160's will handle the extra voltage, but I don't know about the 9303's. I have 170's on the ele's, 160's on everything else. When you run that voltage you need to be dang sure you don't have any binding.

A better recommendation would be 6.6V LifePo's Two 3200 packs should do it. You will need a charger for these and hobbyking.com has one that works quite well. I think Tower has some new 3200's out that would work great.

I also have been running two RX's and two switches, (right, Left) with rudder on right and throttle on left. Do not split ganged servos between receivers.

Don't think power expanders and regulators are worth it, just seems like something else that can fail.

I think that's all I have for now. Good Luck!