A good mechanical connection to your FSR is very important, and often over-looked. The mounting system should do two things – provide a stiff, flat surface for contact, and limit the amount of shear force on the sensor. One of the problems with FSRs is that they can give different readings under the same force conditions, depending upon how they are pushed. This is because the sensor averages out the pressure over the whole surface, and a poorly distributed load will apply a lot of pressure in one place, but not another. To counter this effect, always use a relatively stiff material on either side of the FSR, with a thin cushion between, in order distribute the load evenly.