Summary I have seen a hundred and one spool holders for 2020 extrusions, but they all look way too complicated for what they do, and lack elegance. I set about solving the problem using the minimum of filament, the shortest print time, and the easiest fitment. Here it is. Easiest way to print to avoid needing infill is to use Cura, 50% infill (which is as good as 100%), 0.20. I didn't use any brim or support material. Print in two halves. Flip the model 180. Sink the model into the plater 39mm. Create the Gcode and print. Check that your print has accurately allowed the base to fit the 2020 channel. Flip it back upright Sink the model 22.50mm Create the Gode and print Glue the two halves together and job done. If you want to secure the spool holder to the 2020 then just use a short length of double sided 3M tape.