I agree with Russ, the simple solution is the ladder. Kev used to have one pictured somewhere but I cant find it. Its the simple 3 rung "hook over" ladder that you can buy from BPS, Overtons etc. The best part is that you dont even have to install the bumpers or brackets on them that are designed to keep the ladder out from the boat a few inches. If you hook the ladder on the reardeck of a 02 or 03 (dont know about 21s havent seen one on them but Im sure it would still work) the ladder will be held away from the boat by the wings on the hull, works great as the only parts touching the hull are inside the boat (in the rough texture) and the frame/rungs of the ladder rest solidly on the rubrail on the wing. The ladder is about as "drunkproof" as I have seen and is also very easy for women and children to board from deep water with. Beats grunting and pulling yourself up the swimdecks on the transom and the built in ladders on the jackplate/engine area seem neat but one slip and you can get seriously hurt with all that sharp metal back there. Likewise I also prefer the ladder on the side of the boat as it keeps the un-knowing from trying to use your foil as a step! The ladder also folds flat and fits neatly into the rear compartments and certainly under the front deck.
I'll see if I can find a pic,
RA