I want to keep the front of the camera as stock as possible - unfortunately the choices are drill out the aperture (which is metal) and would require a very sturdy drill press (which I don't have) or mount the HQ camera to the front and cover the nice "made in USSR" ring. Since the latter is non-destructive and I can always drill out in the future, I opted for it.

I'm working on a design that will nestle itself inside the double ring on the front - it's tricky because there are varying heights, and the viewing lens of the TLR above as well. Here's the concept so far:

Green is a model of the camera module - it might be a tight fit, as tinkercad has limited features for fine control I'm finding. I miss google sketchup.

I'll need to add a cut out for the upper viewing lens so it fits, and probably posts for the camera module to press in to. IF I've measured everything correctly, there should be some pressure that keeps this model in place where the previous lens used to be, as well as space to run the camera module cable through the aperture into the back of the camera.  The next question is how to attach it to the Lubitel in a reversible way in case I need to replace camera modules?

Alright - I'll update this post over the weekend once I've had time to print and test fit. Thanks for reading along if you are.