You can search all over but there are not many choices for a amplified and conditioned 5 volt force sensor.
http://www.digikey.com/product-detai...6951-ND/809397
Yes, this was one of the build seasons major crisis. We had both a 3 stage andy mark and a vex pro ball shifter. Looked at both. Choose the andy mark because it could be modified the fastest. Was tested after 1 night's work and we went for it. Looking back the ball shifter is what we should have done but there was no time to devote to it. Make your choices and live with them. Yes, it does take a 1.5 inch pancake at 40 psi to rip the dog out. We replace the dog gear before each competition. I like balls. We also used a ball clutch on our intake roller to prevent RS motor burn out.