whats the biggest, i should say highest mah rating can i get in the cpv3?

You can almost put anything you want in it but at somepoint you are going to run into trouble with no room for the battery and weight issues where you are no longer gaining any advantage and it starts to cost you. I run a thunder power 1320mah in mine and oddly enough it is a smaller battery than the Electrify 910mah that it came with. 

cool, thanks