I would re-think the carpet idea. They trap moisture (not good for the painted surface) and dirt. Unless, that is, you can arrange to roll it up between uses. You could fasten it with some snaps to keep it in place and which would allow you to take it up for quick storage. Chairs: no matter how good the stitching, the padding will get wet and raunchy...so, if you use them, fashion a waterproof cover (Sunbrella or vinyl) for them. Easy to make---just stitched along three sides.
I'll have to look in the garage but I think I have a pair of padded chairs left from my boat sale. They are the sturdy ones with the double legs. Cushions good shape (we always stored inside the boat), aluminum needs light sanding. Let me know if you are interested via PM or email.
Joel Albert, Potomac MD
"Charlie B" - 1988 32' FBS
Twin 318's/FWC/16x15 nibral props
docked Deale, MD