I've actually run LiPo in 12th and I think that LiPo just plain isn't there yet.

The small cells that you need to run a t-bar car can't handle the current. With almost any pack, you'll have less capacity running 2 cell voltage than a good 4600 pack.

I've run single cell voltage (3.7v) with a 13.5 in 12th without a receiver pack. It worked just fine for me but it might be an issue with hotter motors. Receiver packs aren't an issue and not that expensive. I was running a Spektrum system.

2 cell voltage is too fast especially for mod. a 21.5 might work but why should we buy another motor just for the privelage of running LiPo? Think there's problems now with mixing two motors in stock, wait until we try mixing in a 3rd with new batteries on top of that.

The car handled like crap with LiPo by the way. Had to add almost all of the weight back in just to make the car work. At the moment, it's more trouble than it's worth.