Bottom mounted spool holder for 2040 aluminium extrusions

Remixed this stylish spool holder by PhantomGT.

I needed to mount my spool holder on the bottom of a 2040 rail, and since the original requires no screws and is held in place by gravity, I had to reverse the direction of the mounts and rotate the top part of the spindle by 180 degrees.

Have lengthened the arm slightly, added some lightening holes as well as trimming the base section - to help reduce filament used and printing times.

Also if you're running dual extruders like me, you can