Got to take the school's 3D20 printer home over summer to learn how to use it. First things first was to modify it so it could use the 1 kg spool of filament we ordered without realizing it wouldn't fit!
Pretty ugly print. First time the spool adapter didn't adhere and ended up a mess. The holder itself was okay. Good enough to try.
I had the same problem as @Cosmosis where the bolts wouldn't grip after I took them out. This is because there were nuts on the interior ends of the bolts. I ended up taking the bottom off the printer and was able to locate the nuts and screw the spool holder in securely.
Spins okay. Going to see if I can get a better fit on the spool. The kind of filament I had wasn't one of the brands that was listed, so I just measured the hole diameter and spool width and used the model that was closest. It's not perfect but it works!
Thanks @bbeaudoin for the design!