mike, for safety purposes a genera rule is charge at 1C for a 4900mAh, 4.9 amps. I have orion plats and tthey are 4800 and I charge them at 4 amps, although they could withstand 4.8amp charge rate.
return the bag, you wont need it unless you deliberately try to over heat the battery.
use a duratrax ice if you can afford it, they are liek 120-130 depending where you shop.
I charged my lipos before I closed shop last winter. I got back out there in march (maybe april) and topped one of them. it still had 8.4 volts in it and only charged for like, a minute. it was cold and the thing held the charge for 3 months. and no, im not kidding. lipo are faaaar superior to NiMH. and I guarantee youll never go back.
I have never balanced the cells, but if you built a simple comparator circuit, you could balance them yourself.
I saw the sliverado slammer in action when you ran both of PJs lipos in it on that one video.
it sure seemed to have more get-up than i had ever seen before.
for weight issues at Crackside when your racing, you can simply offset the weight difference with a 100g slab of brass plate in the bottom of your battery tray. Thats what matt sunderladge did, and I drove his losi desert truck with that setup, and it seemed fine.
in my trucks, I dont use additional weight. I just got used to the handling differrences.
When you come over again, you can review Erics Hyperion charger ( which is totally over the top) and also if you have lipos, but no chargers yet, we have about 7 ICEs in the house you can always heat up when you get there.
Pete