I posted some internal pics
here. Batteries are 1500/1700/2000mah 5,6,7mm thick... stock is 4.3 thick. stock is 1150mah. I am not confident that these thicker batteries will fit. Notice the picture of the battery, you can see a small pcb inside the wrapping. I think this is the voltage regulator, but I'm not going to cut loose my current battery quite yet. I'm still awaiting the samples for one, I will do a dry fit when they get here, and then maybe I'll take the plunge.
-dvn