The author remixed this model.
The original specifies an Arca Swiss clamp on the output side of the RA drive to the dovetail on the DEC drive. The drive-to-drive model can be printed and the two attached without that additional clamp.
I also designed another output plate that should simply drop in for the original output plate. It allows mounting a different Arca Swiss clamp than the original with M5 flat bolts to M5 inserts installed in the plate. There is more separation between the output plate surface and the drive to accomodate the large knob. EDIT: V02 now has holes that are a better size for M5 inserts and there are two sets, one 30mm spaced and the other 50mm spaced.