3rd antenna up for mounting is the gps antenna from Dynon Avionics. The gps comes with a template that makes the installation of the screws easy. However, I found out after the fact that the wire coming out of the antenna is moulded in some kind of sillicon rubber and the wire was coming out on the side which after cutting the center hole put the wire very close to the edge of the cut out. I enlarged the hole slightly but if I would have known upfront, I would have placed the center hole in a different offset location. Just my 2 cents if you are planning to install one as well.

I started  by making a doubler that will be on the inside of the fuselage and hole 4 nutplates fo the screws.

A gps needs a clear eye-on-the-sky so the best position is on top op the fuselage. I had to temporarily reinstall the canopy to ensure that the sliding of the canopy would not interfere with the gps puck.
In the location drawn below it doesn't. The rear skirt slides nicely over it with lots of clearance.

Here's the doubler place cut and drilled. I checked if the screws were ok through the gps and into the doubler. Using a template is always less precise but it came out very well.

 I used the doubler as a template to match drill the upper fuselage skin. The small #40 holes are for rivets holding the doubler.

 Doubler plate dimpled, primed and nutplates installed.

Here's a shot of the finished product.

Inside view of the doubler plate rivetted to the upper skin.