That is the last setup I tried. You can see the micro switch with a roller, and that grey blob is JB-weld, making a bead that pushed on the switch. This is the last one that I tried, which did not work.
If you look at the driveshaft, there is a perfect spot right after the weld (between the round part and the bearing connection) which should give me 2 passes/revolution of the driveshaft. Fabricating a mount would not be very difficult at all, I would simply make one very similar to the one you can see in the picture.