So I Have a Muggy Now!

I'm wondering, what kind of gearring would you suggest for a Muggy using a 2200kv MMM combo?
I've tried 11/48 (using a Innovative RC chassis, with a robinson spur on the center diff.) on 4S Lipo, it worked quite well, appart from the top speed beeing rubbish.
But when I tried 6S Lipo, the controller became really hot. (I use the same Lipo's in my E-revo brushless edition, with the 18/54 gearing, and that works perfect. so the lipo's are good.)