Using vision has uncovered some annoying details about tuning for the C1 motion platform.

Turns out if an axis not being perfectly planar in it's travel, due to an end-stop being even slightly off, that also throws off the X-Y linearity in a big way.  

So even if you have the machine tracking perfectly along Y, but you have either of the front axis end-stops off by a tiny bit, X will track an angle which is not 90 degrees from the travel you get for Y.

And so just when I have it basically perfect in all directions, I can then detect that my tripod kinematics numbers were off by like .5%.  So I fix that... and it throws off the endstops and axis scale again.  And then while adjusting the endstops, I break one.  So I redesigned them to be a bit thicker where it needed it... reprinted them all... and then started all over.

Blew another entire day on that.  

If people are going to remain sane, I'm going to have to implement visual homing.

Also, my base plywood board I picked is not stiff enough.  With the camera I can easily detect the board flexing if I happen to lean on it.  I'll need to glue some cross bracing in underneath.