For just going in and out through moderate surf, Jeff's boats should do fine. Skin on frame construction is quite strong, though for serious heavy seas work I would go with a traditionally built boat rather than a fuselage frame. Traditional boats have the loads distributed better IMO, keelson and stringer loads are spread over 20 to 30 ribs rather than 6-8 ply frames and your gunwales are generally beefier, at least for the Greenland type boats. Traditional boats are a bit heavier than fuseframe boats...in the real world, most 17-18 ft. Greenlands weight in at 35 to 40 lbs or a bit more. Still much lighter than glass, ply, or plastic boats.
As designed, I wouldn't want to subject a fuselage frame boat to a serious washing machine event in heavy surf, but they are more than strong enough for the use that most people will ever subject them to.
It would be a relatively simple matter to beef a boat up for regular service in heavy conditions with a very modest weight penalty. This is what *I* would do if I wanted to make a dedicated surf boat in fuselage frame style.
First, I'd increase the scantling size of the gunwales....go to 2" wide and make them of doug fir or a good straight grained hard pine. Both are stiffer, and tougher than WRC and much less likely to break. I would also make my keelson and stringers and deck stringers from good straight vertical grain doug fir or similar wood for the same reason. Since doug fir is stiffer and stronger than WRC, you can reduce the scantling size to offset *some* of the weight penalty. Last, I'd peg and lash in a couple of light deck beams between frames both fore and aft. This is simple to do, won't alter the boat's lines or take up any more interior space and adds alot of support to the deck structure. You can make these from WRC or redwood to save weight. You might add 5 lbs or so to your build doing this.
Whatever you do, if you are going in and out of surf, you MUST have good reserve flotation. A fully swamped kayak in surf can be LETHAL. If you are halfway in and halfway out in the middle of a wet exit, a wave can drive you and your semi attached boat right down to the bottom with enough force to kill you. Invest in good quality, properly fit flotation bags.