Wierd. I was able to get dead-nuts 50/50 right to left balance on my TC3 by simply paying attention to how I mounted the electronics.
The problem I see with the additional chassis width is having the chassis drag in corners, especially on rough or bumpy tracks. And all the battery slots would have to take it's toll on rigidity and strength. I'd actually be interested in finding out how much less your chassis weighs than the stocker.