Ted,
I had thought about doing that very same thing with the sensor. After much debate (because the sensors are $45 a pop) I decided I did want a clean, reliable way to mount the sensor to the motor so...
I got the factory sensors, gutted the mounts and cleaned them up. I mounted the TwinSync sensors in the 3W sensor mount, loaded the insides up with epoxy resin and then mounted them to the motors.
-M51
ORIGINAL: F2G-1
Just thinking out loud here....
Looking at your pics, wouldnt it be super clean if you could get another rpm hall sensor and mount from the manufacturer (the one used for the ignition crank trigger) and bolt it to the other side of the crank, utilizing the same magnet?
idono, just a thought.
Or...
I was thinking if I had to use a spinner mounted magnet, to get a half of an old 2 peice nylon engine mount (pref. a long one) mount it to the firewall (with a spacer block on the firewall if needed) with the sensor at the other end by the spinner. This might work if you are using a large diam. spinner.
Ted