There is no equal way to race 4 cell and lipo. The motor combo or wt combos do not work well and the corner speed vrs the accel points are so different it is a very hard battle.

We started testing early this year running 3 cell nimmh and single lipo.... Logically we run a 6 cell or 2 cell lipo in a sedan and wt equal we all have agreed they Are equal on the track. Well long story short 3 cell nimmh and single lipo are exactly that equal... And very easy to balance 3 cells in a tbar car so no reason to feel you need to upgrade a chassis just lop a cell off rebalance and have all the gains of lipo. Lower tire wear and all.

here are a couple vids from our 12th stock 17.5 mixed lipo and 3 cell nimmh. Club size track 36 x 60.
http://www.youtube.com/watch?v=sFyOVqN7oqI
http://www.youtube.com/watch?v=MKjS5Ii1yBo
http://www.youtube.com/watch?v=0NB7q3NQb9k