Just a word of caution/warning before you buy the R/C Monster battery tray.
I've got one in my MBX-6 and I had to jack the body posts up at least 1/2 an inch just to get the body to come close to sitting level.
Even with just a 5000mah pack it is way too high. 6000mah or higher? Forget it.
Unless you don't mind it looking like it's all crooked.
With the spacer and the thickness of the tray itself it just pushes the battery too high in my opinion.
I wish I had a tray that would get the battery closer to the chassis.