Dick:
Far simpler if you forget about the switched side and just allow the brains of the driver to let up on the button when the shade has descended to a low enough height (while driving). Your existing buttons will suffice, you just need to get the power off the switched terminal and onto a terminal that always has power.
This is how mine were installed, by the MCD guy in Indio a couple of years ago. We had a discussion about how they should be wired, and this was his preferred method, as I didn't already have any switches or wires in the front of the Contessa that could merely be repurposed.
I pulled the fabric covered ceiling board down from where the drapery track had been, found a solid bit of aluminum frame up there that things would attach to, and put a wooden valance up that looked like the rest of the woodwork in the coach, so the MCDs were well hidden and looked like they had always been there.