This is where I’m at. I’d like to fasten plumbing hangers, light davitts, panel magnets, controller boxes ect which I’d use stainless Fasteners for so aluminum’s out. Here in Gloucester the commercial fishermen are having good luck with 304 stainless finished with rinoguard which is an additional expense (not sure how much yet). My international paint rep recommended interprotect which is a marine barrier coat for bellow the waterline. If I go with 316 I’d need to hire a welder but would need no finishing. And finally I’m still not sure if my design is strong enough. The photo is pricing and top 48” beams profile