Looking forward to an upgrade of my current project I had an idea for simple tracked running on the 2020 extrusion, could be used on DeltaBots or any build with 2020 removing reliance on round bar linear shafts. As for testing have been using similar on my deltabot for about six months now lots of printing and no problems.
Bearings 623-ZZ 3x10x4 Miniature deep groove
Machine screws M3 16 x 3 and M3 25 x 3
Printed for strength and durability.