Thanks Patrick.

I've done some riveting and I think water can enter the mast both through the hole in the rivet and around the rivet (sleeve) itself. The back of the rivet is shortened/deformed by the pin which is broken off when compressing the sleeve. Sometimes it falls out altogether. Even if it doesn't there's no reason for the remnant in the rivet to keep water out. Also, even though rivets are fairly tight there's no reason why water can't leak in between the hole in the mast and the rivet. So I think the only way to waterproof a rivet is to silicone seal both the edges of the rivet face and the hole in the center of the rivet. I'm curious if you've had other experience.

Jerry