I wanted my I fly to mount about an inch from my panel over a large empty spot. Here's how I did it, mounted a counter sink stainless steel 80* finishing washer upside down with a 1/4 screw or allen head bolt. These washers can be found at Lowes, Home Depot, or AC spruce. I used a fender washer where the bolt goes through the panel for extra support. The adapter provided with the GPS, that clamps over the ball will clap onto the upside down washer on the end opposite of the ball socket end. This setup allows a small amount adjustability to tilt the screen where you want it. I have made several fights some in gusty conditions and it seems to hold just fine.
