Glad you asked. I used high quality 3/8" recessed alarm switches. And special ones with a philips profile, that can be unscewed if needed.
They activate the transistor switched DPDT relays on the logic board. That and a few Diodes are all that was needed for the logic. Each switch on the machine has its own LED on the board making for easy troubleshooting.
Board was cheap, but very high quality from Electronics Saloon on Ebay (China) Two heavier Octal FInder Relays switch the Solenoids. Manual push switches on those can also help to diagnose a problem.

The magnetic reed switches had to both be set away from the steel and be supported in the thin splitter tube structure.
A heavy nylon material is press fit into the small tube and the alarm contact is screwed into that. The welded on washer prevents the nylon material from going too far and get lost forever inside the splitter tube.

A friend machined out the plate and nylon material which accepts a rare earth magnet.
Durability was key and I did not want wires or anything else protruding.
I am not happy with the electrical build quality at all. I simply ran out of room as soon as the hydraulics went in. The machinist friend would have done a much nicer job overall on the fabricating, but hey it works, and works well.