I sealed my awning supports with Aviation Form-A-Gasket and Acryl-R. I am not sure the Form-A-Gasket was the best sealant since it is for closely fitting machined surfaces.
The supports are installed in the worst place they could come up with—over seams in the outer skin and over rivets. The lower support is curved underneath, but does not mate well with the skin. These are not machined to fit closely.
Nonetheless, I used the Form-A-Gasket, putting a liberal amount in the screw and rivet holes on the skin and in the support. Mostly they used screws, but the lower ones had a rivet. When I tried to install one of the screws in the front upper support, the screw would not tighten, so I put a rivet in there. I put Form-A-Gasket on the screws and rivets too.
After I reinstalled each support, I spread Acryl-R around the supports and over the rivets. I'm hoping the two sealants will work better than one. When I removed the supports, I found some Acryl-R underneath, but not over the entire back surface on most of them. One had it smeared over back of the entire part. If Acryl-R had been put around the entire place where they mated with the skin, it had come loose in places, especially where the seams were.
I'm waiting for more snow so I can see whether the seal will work in the back of the trailer. This is where there had been a leak which ran under the vinyl floor. Not only are the supports installed in a bad place, but water runs down the side of the trailer right where the supports are.
My leak was not nearly as bad as some others. My subfloor has not rotted, but does have some water stains. I would not have discovered this had the vinyl not started getting humps in it because of improper floor installation leading me to replace it. I guess I am lucky I live in a cold climate where vinyl does that. People in warmer states would not notice unless they decide to pull up the floor because they think it looks cheap (it is very cheap vinyl).