Thank you for sharing this design.  I like this concept because without this adapter the light meter sits too close to body and lens in my opinion. I would have to take the light meter off the cold shoe to double check my light meter reading.  I printed the accessory with the following settings:  Printer: Ender Pro 3  Filament: PLA  Nozzle Temperature: 200 C  Bed Temperature: 50 C  The adapter came out slightly too wide for the Mamiya's cold shoe and slightly too narrow for the Reflx Lab light meter. That's why you can see it doesn't fit all the way into the slot. However, I believe I can fix both problems with a dremel. I just need to shave off a little PLA on a few sides. I will update this comment when I do.  I'm not familiar with editing CAD files yet. I think that just a 0.2mm difference for each end of the adapter would be perfect. The file is almost exactly the right dimensions.