The instructions indicated that one had to have the switch hold a minimum of 1 inch below the level of the inlet. The instructions also say that one has to have a 2 inch separation between the two holes. Unfortunately the distance from the inlet is such that the hole for the pump needs to be drilled in the extreme bottom of the muffler. As you can see there is no way to attach the plate such that the hole will be in the extreme lower end of the muffler.
Additionally, the curvature of the muffler is such that you can't really just screw the plate on. One would have had to build it up with fiberglass or make some other modification in order to get it solidly affixed.