Oh boy... well, 2 or 3 hours isn't gonna cut it for me. Looks like I'm still in for more modding than just adding the strap. I just went back and looked at a bunch of pics from the V2 mod thread, and yeah, that stock battery is pretty small. Also, I keep going back and forth on this, but in the end I have a feeling I won't be satisfied until I mod my shoes just like Brads, heel cup LEDs, EL, toe mod and all. It really looks amazing.
Also, I agree that a 9v at the moment is the best option, as
a) it powers everything for a fairly long time, and
b) you can easily pop in a new one if you're out for longer than 1 battery lasts.