We installed a Gretz Aero mast and mounting bracket for our shiny new Dynon Avionics AOA pitot probe in the rib bay just outboard of the aileron bellcrank bay. We pretty much followed the directions that came with the kit with a few exceptions.
Since both the bottom and top skins were only clecoed on, we first removed the top skin to get access to the inside of the bottom skin. We had predrilled the rivet holes in the support angle for its attachment to the backing plate and the rib.
We then placed the backing plate in position with the joggled end inside the spar flange, placed the support angle flush with the rib and we marked the position of the support angle holes on the backing plate. We then flush riveted the support angle to the backing plate.
Then, using the template in the directions as a guide, we marked and drilled the rivet holes on the bottom and side of the backing plate. The backing plate was then returned to its position in the bay with the angle against the rib and the juggle on the spar flange.
While holding the plate in position, we drilled through the four rivet holes on the outside of the spar into the backing plate joggle and clecoed it in position.
Then, from the inside of the bay, we drilled the side and bottom rivet holes in the skin and the rivet holes for attaching the angle to the rib, using the backing plate and angle as a guide.
With these holes clecoed, the backing plate was then used as a template to drill the #19 holes for the screws and to mark the cutout for the mounting bracket. The plate and angle were then unclecoed and the skin was removed to ease cutting the hole for the mounting bracket.
We cut most of the hole with a Dremel tool and worked to the line we had marked with small files.
Once the bracket was fitted, we deburred, dimpled and installed the unit for a final check. It fit great.