I just picked up two SMC 1200 mah packs and an additional battery tray. The method I used to install the batteries on the tray was to... 1.) Cut the manufactures shrink wrap off (as Aaron pointed out ealier).. 2.) Then I actually sanded the battery trays just slightly on the left and right side. 3.) I then took the two pieces of about 1/2 inch shink wrap and "banded" the front and back of the battery on to the battery holder or you can use tape. 4.) After this "normal" step, I went ahead and shrink wrapped the whole tray and battery.
The "light" sanding on each side of the battery tray allowed the additional shrink wrap to still fit into the chassis and create the naturally snug fit, but in this way, I can ensure two points I was aiming for.. I keep fuel and dirt away from the battery and it's connections, and the second point is to reinforce the battery so during hard hits or flips the two bands alone at each end aren't the only holding force on the battery potentially putting a strain on the connection joints (solder tabs or spot weld connections).
Well see if it actually works :-0
