Both the seido 3500 and htc extended 2150 are almost the same size. I would love to find a way to trim off just a tiny amount on my 3500 so that it would fit with the 2150 extended back case. Right now as it stands I can close 3 of the 4 sides of the back cover but the 4th side is a hair off from clipping in. Could peeling the label off and maybe sanding down (ever ever ever so slightly) the battery be a dangerous thing? BTW I know the"corporate" response would be not to tamper with anything but what about a practical answer, could it work?