I've just received a set of ten strain gages that I'm hoping to use to replace the force-sensing resistors that I've thus-far been using to measure the rider's (my) weight distribution.
The force-sensing resistors have worked quite well other than the fact that they tend to slide out from between the deck and the frame. Another issue is that the circuit I've been using to drive the servo amp doesn't have enough gain to be really effective.
The strain gages will go on the frame's crossbars, and I'll remove the mounting bushing at the center of the deck, so that the weight of the rider will be on the crossbars. The gages will measure the miniscule flexing of the crossbars and a pair of instrumentation amplifiers will amplify this measurement to a level where it can drive the servo amplifier.
It takes a good bit of finicky prep work to mount, hook up, and seal the strain gages, but I will post an update when I've got them installed, and another when I've got them driving the servo amp.