The wall thickness on the 3d print ended up being ok. It's still thin and I'll increase it for the next print but another problem arose as I set everything up.
In my attempt to decrease the overall height of the viewfinder I forgot that the ground glass on the camera has a minimum distance to avoid vignetting. It's called a 'waist level viewfinder' for a reason :) and I had the CCD lens way too close.
The result was terrible vignetting on the receiving display. I've increased the height and moved the CCD lens up about 4 cm. The CCD mount, biconvex lens fit, and other dimensions are very good.