I run the 40C Blue and Sky Lipos also with great success in 3s,4s,6s

I've been running my mini stock with some headaches but no smokes. The stock esc will handle 4s in nimh mode but has a low rev limit (depending on gearing). Diffs have been good to me, the trouble comes when you take them apart changing the fluid (who cares on a mini) and strip or over tighten the screws. 2s2p 2200, 3s2p 1550, 4s 2200. Some guys run one lipo and put the esc and Rx in the other lipo compartment, IDK why.

Inran with the esc and rx in the battery tray. It lowers the center of gravity. Also makes adjusting the slipper or changing gear ratios much easier without that huge rx box in the way