Well I got a little more done tonight. Finished the battery tray, added the straps, padding, velcro and bolted the tray to the chassis. The straps are held down using steel washers that have a rubber pad bonded to it, this setup holds the strap but the rubber pad prevents the washer from cutting into the velcro. I have a picture showing how a 4S NeuEnergy lipo fits and another showing how a Zippy 4S also fits, with the Neu being fatter and the Zippy being much longer. They both fit with no problems.
NeuEnergy 4S lipo pack
3M dual lock Velcro on the battery and tray keeps the battery from sliding around.
Zippy 4S lipo pack