I think I'm going to order 2 2S neuenergy batts and pair each to my 3S for a 5S setup. I like the power of the 6S on 51/20 gearing though :).
Castle Neu 1520 on 6S LiPo Powered Gmaxx (Nitro Killer)
Predator with OS .21TM
Supermaxx with Mach .26
Revo with OS .18TZ
Kyosho ST-RR Conversion
Ofna CR with Tekin ESC/Motor (2)