I made an adjustable Z-Endstop, which you can use with a M3x30 screw and a M5 with hammernut. You also need an M3 brass insert nut for the inlay. It's made for an 20x20-Aluprofile. Counterpart of this endstop is the endstop-switch, to mount on the hypercube-frame to generate the z-min-stop-signal.

I attach the original FreeCAD-File for changings. Have fun.