I mounted my prop valve to the subframe and the knob protrudes through the floor board just in front of the driver's seat. You can only see it if you are looking for it. Here are a couple of pictures:
http://home.earthlink.net/~kjcooper1...ebot-sized.jpg
http://home.earthlink.net/~kjcooper1...alve-sized.jpg
I don't plan on adjusting it a lot. I mounted the valve in this location to clean up the engine compartment.