Popped out another one with the scratching head as only 2 pieces instead of 3.  The trick with the scratching head is 5mm retraction & no extra prime.  Everything else continues to work best with 3mm retraction & 1mm extra prime.

It takes a tricky blender boolean to get the alignment notch to come out.

It became clear that a radically different design is needed for bed.  It can't have the head scratcher end.  It needs to be a lower profile.  It needs to be less aggressive.  A more traditional design might be needed.  So far, the mark 1 lion paw has been the best solution.