I went back and forth about where to install this darn thing. If I followed all of Garmin's limitations for min distance between components, the only solution would be to have a couple of antenna magically flying in empty space about 6' off the fuselage.

Long story short, I asked Levi at Midwest Avionics, where he suggested I put this antenna and he said as far away from comm antennas as possible. I asked about just aft of the firewall near the fuel vent because other people have reported good luck at this location and he was concerned about a conflict with it being too close to the engine sensors. However, SteinAir does a ton of RV panels with both Dynon and Garmin panels and they have a diagram with suggested antenna locations. They definitely suggest the fuel vent adjacent location.

I decided that was probably the way to go, so I went ahead and installed it there with a small .032 doubler. The skin is .040 there, so I don't feel the need for a huge doubler. I haven't match drilled the belly skin to the doubler yet. My plan is to get into flight test and confirm that I don't have any problems with this location before I poke a bunch of extra holes in the floor there. If it doesn't work, it will be relatively easy to patch up the holes, and if it does, I'll permanently rivet on the doubler at that point.