Haz. Duralac is that tube of goo you want for your stainless and aluminum fittings. It comes in a white tube with yellow stripe for about $30 and will last you forever. I lay all my fittings and rivets on a board and painted any surface that touches ali to ali or ali to ss (different grades of ali are just as corrosive). Let it dry and then bed all rivets and fittings in a generous amount of sikaflex when you put them together.
Sounds like over kill but every failure I have seen on old boats and ships has involved electrolysis. It will also make it easier to waterproof your mast section.