PAS fixed to gates rear sprocket?

[LithiumFan]

I am thinking of getting a bike with a pinion gearbox but want to fit a rear hub motor so I need to fit a PAS. I have bad knees so really don't want a torque sensor. I have been very happy with Xiongda 2 speed motor which I have had on a total of three bikes, doing the conversions myself, and have done over 7,000 miles, a lot offroad as well as tarmac. I really want to use the same type of motor. With the pinion gearbox it doesn't look as though I can use a PAS sensor at the crank because the gearbox is flat. If anyone has succeeded in this please post with what they did.
Looking at pictures of rear axles with a Gates belt sprocket it does look easier to fix a PAS there. It would just need a longer cable which I can sort out. Is this possible?
I have seen a Geeko hub motor with a cassette based PAS sensor but I have feeling it would not work on a different motor... Also I love the 2 speed system on the Xionda as I can get up almost anything.
Please, no comments about why I should use a mid drive. I have one but much prefer just having a fixed power level I can control with my thumb which I use actively to get a great range. Last Sunday I managed 36 miles on a 36v 6Ah battery on the Traws Eryri route from Betws-y-Coed to Conwy. I am not interested in speed. I often go up hills at just 5 or 6mph in low power in a low gear. Pushing or using the walk button where necessary.
Cheers.

 

[saneagle]

If I were doing it, I'd glue magnets to the back of the chainwheel and either glue the sensor in place or make a custom bracket for it that holds it in the right place. The magnets have to go the right way up and the sensor in the correct orientation too, so test it first to see which way round things go. You can push the magnets out of a normal magnet disc or buy them from Ebay for not a lot.