Thanks Brad for the quick response.
I thought of the rusting thing but the guy at the shop told me that I should use steel since this holds the mast and sail and i dont want this to happen again while sailing.
I know that the pressure is mostly on the 2 shroud and forestay wires since this is what holds the mast up, but heck he's doing this for living so i figured he probably knows more
He sold me what he called (High Performance steel rivets), I know he probably added the High Performance part. HA!