On the whole LiPo thing, I've run both single cell and 2 cell in 12th. I can say from running that single cell will do 2 things for a 4 cell class. But, I don't think that single cell LiPo is the savior that some are expecting it to be.
The up side of single cell is that it slows the classes down so that new racers can run stock. It also slows mod down to a point where it's fun again and 13.5 is a reasonable speed for the guys that don't want to go slow.
The only real problem with single cell is that it needs a receiver pack or voltage booster. The voltage booster isn't a difficult circuit to design so that will probably be the way to go.
The plus side of 2 cell is that no receiver pack is needed.
Problems I saw with 2 cell in a 4 cell car were low capacity, too much speed, and the batteries couldn't handle the current of anything but stock and 13.5. 2 cell and a 21.5 motor is probably too fast for a beginner and we need new racers.