I like what you are trying and doing and
of course im interessted in the usb mod (if it isnt too much trouble).
How sturdy is the usb magnet connection?

Did your camera gain dark corner spots, because of the "spacer" or did it fit?
Did the sd card still work, after lifting the magnet?

Do you know if your samsung battery has build in protection? Did you solder it? The size seems nice. Is it 1500 mah 4.5 mm thick?