A friend of mine had a similar problem when he switched over to Edstrom valves, but came up with a novel idea. (This would be a lot easier to explain with pictures, but try to follow me) He cut about 3" square blocks of wood from 1x4s, drilled about 1.5-2" holes in the center of them, attached hardware cloth to them and mounted them (with the hardware cloth on the top side) on top of the original hardware cloth. Then he cut out the 1.5-2" hole in the original hardware cloth and mounted the sipper valves to the new hardware cloth on top of the wooden block. This way the valves don't stick into the tubs, and they can be pulled out all they with no problems. Did that make sense? If not I'll see if I can get some pictures from him.

-Evan