Edit: Ugh I really need to figure out why my STL previews show up rotated wrong. Regardless, Rotate the model on the X axis 270deg.

For mounting GPU face down or standing up. Mirror it to mount it face up.
Works great for Wire frame shelving.

2 slot width cards will have almost 3/4" of clearance below card and surface you mount it on. Images are from my first itteration. The uploaded files are revised to be more space efficient, allow 3 slot cards.

There are 5 spacer files for different thickness cards. 0.2", 0.4", 0.6", 0.8" and 1".
Dual slot cards will probably use the 0.8"