Yashica Mat-124G vertical Cold Shoe Bubble Level

I recently acquired my first vintage TLR camera, a Yashica Mat-124G. Since I haven't yet gotten used to the viewfinder being mirrored, I find it particularly difficult to control the tilt of the camera to capture horizontal or vertical lines. 

Since I had a couple of small bubble levels lying around, I thought I'd craft myself a little aid while I'm still practicing.

The bubble level just press-fits into place in my print, you may have to put in a dab of glue or widen the slot a little, depending on the accuracy of your printer. 

After assembly, slide the print into the cold shoe and place the camera on a flat, level surface to check that it is indeed displayed level. If it is not, the cold shoe might be bent slightly. To mitigate this, you can either install the bubble level at a slight angle into the print to correct the "skew" or try to carefully bend the cold shoe so that it is perfectly vertical. However, bending and thus breaking parts on your camera is done at your own risk. 

Edit: I added a second version, featuring a cold shoe, so you don't lose the ability to mount one of those small light-meters, for example. The cold-shoe's dimensions work great for my flashes, let me know if you find it too loose. 
Redid the whole model, optimizing some dimensions to fit my Yashica better; I don't know about the fit on other TLRs, however. 
Pictures will be added soon™.

It's by no means beautiful, but it's practical and gets the job done for me. Feel free to build upon my idea if you find it useful!

Additional Hardware needed: one 12 mm bubble level like this one (obviously).

Printed in 0.2 mm lying on the side without supports, as pictured in the last image.