This is a hacked together overstuffed spool holder that may almost double as a handle for the X1 when no spool is loaded.

Looking at the spool on my printer currently, The upright could probably be 20mm shorter and still function quite well.

I would also mention the uploaded model moves the upright 10mm closer to the Z axis and the holes for the screws were enlarged to allow them to countersink meaning the original screws should work to hold it on.

Yes

40 to 50 percent

I used 6 top and bottom with 6 shells.

It was a LONG print on my X1. I had some filament issues and filled the missing bits in with superglue and baking soda then sanded it down to be smoother. I wasn't going to waste the plastic and the print time, again.

OpenSCAD was used. Just unioned a bunch of blocks together until I was okay with what I saw.