I go to WW Granger and buy a NPN prox sensor and mount it on the rear wheel. I count the 6 brake rotor bolts. Works great on the rostra. The big advantage is you can shift and still hold the same speed. The rostra electric one works better than vacuum at altitude. I just buy the RT cover, spring, and cruise wheel for the splitter box. I just drill a hole in the box for the ball end. Make sure to shorten the cable housing on the rostra, or you will end up with all kinds of problems that look a lot like electrical, instead of mechanical.
For the switches, I use the lever looking one. I but a ballon over it to water proof it. This is the easy way to do it.
For the brake light wire you have to use a relay, if you have an LED tail light.
I do not use a switch on the clutch lever. That back up is the rev limiter and kill switch. Just use the brake lever first.
Good luck, I love cruises on my bikes. Crilly