[BrianG]

First of all, I'd make some type of flat plate mounted on top of the right servo mount all the way to your current "receiver and antenna mount". That will give you lots of room for batteries, the receiver, and controller etc. You might even do the same for the other side so you can balance the weight by putting batts on each side. From experience, I would try to arrange the batteries so they have plenty of support - so put the somewhat near the front since there is more strength there (unless you re-inforce it somehow). The motors are layed out more to the rear, so that should help lateral balance.

Jusdging by the receiver and antenna layout, you probably have a damaged antenna wire. The wire looks ok, but the actual metal wire inside the insulation could have a hairline break causing sporadic connection, which would explain the problems you are having. I had a brand new Spektrum receiver with a broken antenna wire and it was doing weird stuff so it can happen.

As far as the A123 charger is concerned, it may need to be fixed. Or, pick up a charger that does Lipos and A123 cells...