Kossel 2020 Frame with Detachable Motors

I modified the original Kossel 2020 frame base to add a solid 3mm fill in the area between extrusion "arms". This is meant to provided added stiffness in order to compensate for the other change: I cut out the motor mount into a separate plate that can be dropped in and secured. The fit should be pretty tight, and I've added a screw-down cap to keep the motor mount in place.

The goal here was to allow me better access to mount the motors, or even to switch them out (from 1.8 degree to 0.9 deg