RE: Single Battery Gas set up?
Troy Built Models sells a device that claims to allow single battery operations for the very reason you state. I have not used the device, nor do I know anyone brave enough to try it. I agree with BW's statement, "never sacrifice safety for performance." If your that concerned about weight you could run two small 2 cell 500 mah lipos and charge them after each flight. Also, I don't what kind of regulator you are using but the little Castle Creations regulator is very light and can handle 10 AMPS, you may be able to save some weight their as well.
Regards,
Tom