Matt, It is a good idea to have a rub rail - I wish I'd put one on when I built our boat. The suggestion of half round ss pipe is excellent, as it does not have a ledge underneath to catch on other boats if you are rafted together and the water
is not dead calm.
You will have to continuously weld it so that the void inside is airtight. Beware distortion of surrounding plate.
Another way to do it is to weld short lengths of heavy stainless angle vertically and then bolt a heavy timber section to them. Less welding and replacable but rather crude.
For all deck fittings, make up bits of ss stock, drilled (not right through) and threaded to whatever you want and weld them into the deck.
For the genoa
track I set them into the deck, for the stanchions, they are just butted onto the deck and stand proud.