Derived from https://www.thingiverse.com/thing:39693

First printing... didn't work quite right:
1) I need to make it just slightly longer and wider so that the RPi can more easily fit. This mounts on a wall and thus the holder cannot flex that much.
2) The notches in the 4 corners need to be a bit higher off the surface and the notches a bit bigger vertically, again so that the board can more easily fit.