[lincpimp]

For balance on the maxx 2 packs are preferable. You can run a pair of 2s packs for 4s, or a 2s and a 3s for 5s total. Best to keep the same packs together, as all of the cells will age at the same rate if always run together. I would go with 5s, 4s setups tend to have high current draws, and 5s will allow for lower gearing (for the same speed if using the same motor) and you will get longer runtime.