The problem isn't so much dinging the hull when getting back onto the boat after you have righted it... it is getting up on the hull when you have just gone over. A friend of mine has all sorts of hack marks on the bottoms of his hulls for that reason. This is a problem with lighter boats because it doesn't just scratch the gelcoat, it dents the outer skin.
I try to be extra careful and roll as I get on the boat.