My original plan was to mount the batteries under and perpendicular to the drive shaft. The packs I ordered will not fit there. So, I think that I will stand them up like you see in the pic, close to center and parallel to the drive shaft. In order to do this I had to re-visit the grinder to carve away some plastic of the diff housing and shorten the radio plate (I figured this would need to be done anyway). I'll also need to slightly cant the servo box (which I've modded into a receiver box) to the outside of the chassis. No big deal, really and the placing for the rest of the electronics will be left.
The way I have everything set up, I will be about 100g or so heavy on the top, motor side of the chassis.