CNC support foot for 20mm section frame

My cheap Chinese 1610 desktop CNC router causes a fair amount of vibration, and sometimes that means it also tries to walk around the table! So, I decided I needed some support feet for the four corners, with a flat area underneath to add some rubber or felt feet too.

This project is my attempt at that. When printed they should fit snugly into the ends of the 20mm-section aluminium CNC frame pieces, at each corner of the base. It should work with any 20mm-section frame on other similar CNC mach