Maybe I should just do it, since this thread is generating some good debate on whether or not it will work. Problem is, I'm a cheapass and don't wanna spend $50 on a Zippy 5S pack.
I may end up just going with 4S/8XL. That worked well in my old E-Revo. Sure, the motor runs hot, but that's what my leftover HV heat sink is for. And I already have four 2S packs to play with.