The Dynon GPS will go on the top skin behind the baggage compartment. I didn't have enough aluminum sheet stock to make doublers for all of the antennas, so I ordered a bunch of .063" sheet from onlinemetals.com. Given that they have a location in Seattle, it ended up being a great way to go. I'll have to remember that for the future. I cut out a doubler just a little bigger than the GPS puck and drilled holes for the rivets to the skin and for the nutplates for the GPS screws. I had to put a slight bend into the doubler to match the skin.
The other GPS (Garmin) will go a little further aft and to the other side of center. For whatever reason, the installation instructions for GPS antennas say not to put them on the center line, hence the reason they're offset. The second antenna also needs to be at least 12" away center-to-center.
