Candace,
I am chuckling about the concept you raise about the walking foot hitting the pressure foot lever. The Singer walking foot that broke had that problem. My solution was to use an extremely large rubber band positioned around the pressure foot lever and the pressure knob on top of the machine. It lifted the lever slightly -- just enough to give clearance to the walking foot, but not enough to actually raise the foot.
Concerning my current problem -- I am just going to have to try different models until I get a good fit.
Dayle