So instead of deciding between the boxy shelf and the triangle shelf, I decided on making it convertible. I did this by separating the “arms” from the main shelf as shown below. It took a while to get all the measurements right but I finally perfected the rotating part. Now I need to add holes in the arms for the plates to slide into, I’m gonna try to add something to keep the arm more steady when it’s in the triangle shape, and then split it into pieces so it fits on a printer bed!