Yes, I recommend using carriage bolts that you suck down beneath the surface of the wood. You also need to use regular nuts with a lock washer, as nylock nuts will put too much tension on the carriage bolt and not allow it to suck down into the wood. Then I went back and installed a second nut. This way if you had something coming loose, it was always easy to see if one nut was missing. Of course, use all SS hardware.

Never had a problem with treated lumber and galvanized lags in fresh water. My Prestige and all 3 of my Heritage trailers came with treated bunks. Yes, the galvanized lags will rust and yes, after a couple dunkings they tend to back off a bit but after re-tightening them they stay put. I'm going on 6-7 or so seasons on my current bunks/lags and the lags are still holding fine. The carpet wears thru and needs replaced before any of the lags give up the ghost. At that point I replace everything (wood/lags/carpet). I'm not about to pull a bazillion staples out!

Yes, this is a better idea, Ipe is mofo strong sh!t Built a deck from it last summer...eegads...like steel. Wonder if they make 2x6 Ipe, that would be the ticket.

interesting....I am surprised that with the chemicals that are now being used to treat pine that there would be that much reaction with galvanized hardware......I own a Cypress mill and the problem with it is it's tendency to float....I had Cypress on my lift bunks and had to add a quite a bit of weight so the lift would sink........might be fine with the weight of a trailer....IPE maybe a great choice as it is extremely rot resistant and quite heavy.......but it is very pricey