I used the 3M doubles sided foam adhesive to attach my new cell and WiFi antenna to the top of my Class A motor home. I also used it to attach a junction box to the roof where I cut a hole to chase the cables through.
I followed 3M’s instructions to prepare each surface by sanding
with 200 grit sand and then cleaning with alcohol.
When I attached the junction box, I was a little hasty and the box edges are at a slight angle to the horizontal and vertical - absolutely no way to remove the junction box once it was attached. I am confident that I don’t need screws to hold it in place and, consequently, don’t need Dicor around the edges. The same situation applies to the antenna (which is mounted on top of a tall junction box) to get above the decorative/awning railing of my Newmar Dutch Star - no screws, no Dicor. Have not lost the antenna even with it facing a 60mph “breeze”.