The maintenance seems to really increase running the Flux on 6S, I've had hardly nothing go wrong on 4S until I started running 6S as a steady diet. I have twisted dog bones, killed slipper pads, sheared a drive cup and chewed up pinions running 6S - never did that running 4S.

If you buy the same capacity and C rating 3S lipos (same brand preferably) as your 2S, you can run one 2S and one 3S lio as a 5S combo. Thats what I've settled on. Its faster than 4S and isn't quite as bad on parts as 6S seems to be.

To run lipos in series like on a Flux, they have to be the same capacity and should be same C rating. Ideally, they chould be the same age or useage too.