SC8UU mount for 2020 extrusion

I've built a larger than usual i3 style printer, and made the y carriage from leftover 2020 extrusions from the old smaller frame.

This part mounts SC8UU bearings to the bottom of said 2020. The fit is pretty loose to avoid distorting a Drylin bearing. Carefully tightening with an M3 screw / nylock will secure them well.