External Battery Holder for Phantom DJI

I wanted to design a Battery holder for carrying 2 Batteries without doing any change to my Phantom. The new Battery Cap is still in progress, and I will add it later. If anyone got a good Battery Cap model, please let me know :)

Jan 6th 2014
I just added my design of the battery cover with two openings for the connection. I leave it now there.

Jan 8th 2014
Added a top for the battery holder as tempeature protection. First flight in a cold surrounding showed that it is neccessary to c