The Garmin GMU 22 magnetometer is mounted into one of the lightening holes on the aft deck of the fusalage where the horizontal stabilizer is mounted. I purchased my mounting plate from Stein Air and have to do some fabrication work. I centered the mounting plate over the right lightening hole on the aft deck with the mounting arrow facing forward. I marked where I needed to trim the right side of the mounting plate to clear the longeron rivet row. I made the cut on my band saw and deburred the edge. Next, I carefully measured the orientation of the mounting plate and marked the perimeter with a marker. Then, I marked the rivet locations on the mounting plate and drilled those out on my drill press to 3/16". I placed the mounting plate back on the deck and clamped in place with a c clamp. I match drilled the holes to #30. I deburred the holes. Last, I cleaned and primed the mounting plate and the aft deck with self etching gray primer. I will rivet the mounting plate later, after I have the lighting, trim and magnetometer wires run.
