Thingiverse is currently experiencing issues related to search. We are currently investigating. Thanks for your patience.
Just finishing up my last motor mount on this. I had to upscale it by 1.015x because the extrusion was too tight to fit even if I sanded it a bit. Printed in PLA.
A suggestion: The motor mounts could perhaps have the slots for a 20x40 extrusion and therefore the builder could use either 20x20 OR 20x40.