The reason why 1/12th went and were happy to, was that there is a core group of 12th racers and are happy to, it isn't the same as TC, it is like comparing Apples and Cows....
It seems to be, the problem isn't outdoors but indoors, so heck, run johnsons, I would if my club made it so, for small tracks, I will run the fastest they allow on that day, and won't moan about costs, cause I don't burn things out, I run a motor specificaly so that it don't chew brushes. I wouldn't go 5 cell, as I am not pulling cells apart then have to put them back together for the buggy, sod that for a laugh.
Amp draw and cell count. now, lets say a motor can take 80watts of power, it will take that whether it is 5, 6 or 7 cell, the more cells in a car, the less current draw per cell (P=VI if I remember), so less cells mean higher current draw which will, instead of cooking a rebuildable motor, will pop an unrebuildable cell.