I wished I had done this before installing the OHC the air manifold and the OHC itself made drilling holes problem. I turned the canopy over so gthat it was right side up and located where exactly I wanted the 2 GPS antennas. I then used a template to drill holes for the mounting screws and the BNC/TNC connectors. I then discovered that the canopy was thicker than I expected which would cause a problem trying to connect the RG400 to the antennas because the canopy was thicker than the male connectors on the antennas. That meant that I had to create space somehow to in order to be able to connect the female BNC/TNC connectors on the RG400 to the male connectors on the bottom of the antennas (they sort of screw on). My solution was to rout out the honeycomb from the interior insuring I didn't cut into the outer skin. I orignally was going to remove enough material so that I could use the mounting hardware that came with the antennas, but I as I was having difficulty removing material as I moved closer to the OHC, I decided to just replace the hardware with longer screws. As a result, I went back in and filled in the cavities, less the area required for the connectors, with flox.
