Actually, I didn't actually measure them, so you got a good point. As far as damage and how much juice they can take? I'll find out when I try a 9V battery mod next. I haven't noticed any handling problems except when I go into a turn too fast, I flip sometimes.
demonracer, I would pick whichever of those is the smallest or closest to thge wire size you are using. You should go into a RS store and see what size they are and go from there.