Yeah this is also very nice. The thing I miss most when using the mugen cover is the camera cover.

But using this you need to secure the outside battery as I afraid it may come off if too much force is applied.

Waiting for your final solution

BTW, I think you don't need to connect the test pin, as this will reduce the inner resistance of the resistors, which will result in lower mAh reading. For more info please see these link:
http://www.cpkb.org/wiki/Nokia_BL-5J_battery_pinout

http://www.cpkb.org/wiki/BSI