RE: MPI switches
I have used both the MPI and the Radical switches, both with great success.
However, the Radical switch uses a plastic backing plate inside the plane that you screw 2 sheet metal screws into.
The MPI switch uses tiny bolts, nuts and washers with no backing plate.
There are several of those tiny nuts floating around in one or two of my planes.
I like the Radical switches better, if only for this reason.