[angelah]

We are attempting something similar. We looked at these options, but then we realized that a two cylinders, each controlling one end of our mechanism, gives us three positions if we don't mind the middle position "opening" being off-center. This seemed okay because it will only carry the weight of one object in its middle position (you don't stack anything on top of it anyway.) Not sure how it will work out, but that's what our solution is so far.