Damage Repair

Last weekend, I started sanding the paint off of the bottom edge of the trailer so that I could reapply epoxy to the end grain of the plywood. But it was bothering me that I couldn't figure out how the water got in so I asked for advise on the trailer forum. Someone had a very good theory on what might have happened. The trailer walls are attached directly to the metal frame with screws. Even though both sides of the walls are sealed with epoxy, I broke that seal when I shot the screws through the walls. The theory is that the water came in through the screw holes. When I attached the walls, I should have put silicone or something similar in the holes before putting the screws in. Obviously, it's too late for that now. I have been advised to remove the screws, seal the holes and then replace the screws. While I do totally respect the opinion of the person that gave me this advise, I think that this is a very radical procedure considering there was only a very minor amount of damage. I intend to get under the trailer and use silicone to seal around the screws where they are sticking out from the frame. I will also seal all of the joints where the wood touches the metal. If that doesn't work, then I will proceed with the advise I was given.