I installed mine (day/night 4 inch model) with marine
silicone and screwed through into a 1 inch thick jarrah wood backing block on the hatch
underside also cut to accept the 4 inch vent housing. According to the instructions unless your hatch is thick, they sell an optional backing plate accessory for the vent which sticks down into the cabin
, or you can simply make one. This protects the underneath of the vent/fan gizmo from getting whacked by something in the cabin....like your head
No way would I simply glue on a vent over a 3 inch or 4 inch hole in the hatch, 3M 5200 or not. Screw it in. And silicone is used because I am under no illusions that the fan will likely need to be replaced probably sooner than later, and it's much easier to remove by breaking a silicone seal and removing 3 screws than trying to pry off 3M 5200. It's not a below water
throughhull that only needs replacing once every 20 years. It's a plastic fan, a plastic solar
panel, and a thin stainless steel
skin for looks.