I looked back to see if you mentioned your tacho sensor, sorry if I missed it. I mounted mine under the cover using a bracket similar to an alternator/generator arm. My sensor is optical, I painted the very end of the spindle just before it leaves the headstock and added a line. I've read of lots of lathe owners super gluing a magnet to the spindle for a magnetic pick-up, but I have awful luck with supergule, regardless of the quality of the product.
Ron