Hmm, I also have the Logitech radio panel. In fact I have used SPAD to use it not only as a radio panel, but to set my barometer, control the knobs on the G1000 etc and a whole lot more.
One thing you must absolutely do though is uninstall the Logitech driver. It will prevent SPAD from working as it should.
You could try either the C0nnex radio panel device snippet - that mirrors the basic functionality of the or one of mine, if you want some bells and whistles.