As you can see in the photo, I took high density foam and stacked glued it into the inside of fin with the hopes it will help keep the cockpit accessible if plane is on its back. I believe a roll bar just behind the head mounted in the hard point of seat belt will be incorporated in my build also. With these two added safety features in a nose over in dirt or mud your chances are 2-x better to get out of the plane. Plus, no need for ply covering the fin if made solid with foam and med fabric.