With the Infineon 4110 controller, I get 19 mph up Doggetts Wood Lane, 22 down. To make it work, I have to connect the controller's YGB with the motor's BYG. The maximum current draw was 42 amps.
Then I tried the sensorless controller. And it wouldn't work! Eventually, I realised that even if you tell it to allow a minimum voltage of 16 volts, it still decides that 32 volts is too low. So I gave it 10s of battery (37 volts nominal), and it worked fine. There's no hesitation on start-up, and I get 19 mph uphill, 22 down. The maximum current draw was 40 amps.
And finally, the original black Chinese controller. I had to do some work first, to make the connectors compatible with the Infineon, but after waving my soldering iron around for a while, it was ready. My idea for taking a voltage feed from the throttle/blobmeter worked. I also got rid of the handlebar power switch. There's no point, if I want to power off, I unplug the battery. Or use the switch that's near the batteries.
For the test run, I used 10s, and got the same speed as for the Infineon. The maximum current draw was 32 amps, that's the controller limiting the current.
So I left the black Chinese controller in place, tidied up the wiring using lengths of inner tube, curly-wurly cable tidy, and plastic cable ties, and now it looks very neat.
When I go out with it, I'll take the sensorless controller with me, and a couple of 2s batteries. I reckon that if I need to, because I've made them all plug-compatible, I can switch over controllers in the middle of a muddy field, no tools will be needed, and it should take me perhaps 10 minutes.