Very interesting project. Just looking at it indicates to me that it has possibilities. I'm not going to second guess your building methods...just say that the o-ring pistons look good. One question about the foot operated teeter. How is it mounted to remain in a solid position which allows one to teeter it with the foot? This project is interesting to me for many reasons...not the least being that I peripherally work with many different kinds of pumps...including diaphragm pumps....meaning I have access to many various parts. I'm also one of those guys who persists in reinventing the wheel. There's just gotta be a different and better way I can make it roll....