Camera battery grip (Prototype) for GH-1

I'm currently designing a 3d printed battery grip for the Panasonic GH-1.
Due to the complexity of the model,
I'm currently starting out with a highly simplified design.
This prototype only contains 2 batteries, no button, no electronics, no display, no connectors.
Not even routes for the cable. Just holes to mount tiny, 1mm thick copper plates for the battery contacts.
It is opened and closed with 3 M5 sinkhole bolts.
I want to get this prototype right before refining it into a "proper" b