Spiral Binding Cover

This is a simple cover to use with spiral bindings. I tried to match the 4:1 ratio for US spirals and it worked well on the tests I did.

Included is also the scad file because I wanted to learn/do a customizer.

You can add title, but currently only two fixed lines. If you download the scad file you can emboss/raise the text, that option doesn't appear on thingiverse's customizer yet.

TODO: use actual math to generate the role pattern instead of weird measurements taken from actual binders.