Hello, Door retainers were installed on both of my Trilium 1300s.
Drilling the holes in the body was the hardest part. I used tape wrapped
around drill bit to keep it from penetrating the ensolite on the interior.
Then I carefully threaded in self tapping pan head sheet metal screws
a short way so as not to penetrate the interior. The screws were then
cut with a hack saw to be just long enough to engage the fiberglass shell
properly. Small butyl tape pieces were used as sealant.
The door holder works fine and has withstood quite gusty wind conditions.
Good Luck, Larry H