I use a boomless mainsail from a Gcat, it's way shorter than my Hobie's original and allows me to take novices out without them getting knocked in the head. I raise it all the way up the mast, putting it well above everyone's head. I still get good speed as the winds pick up, although it tries to curl up in winds over 20kts. It depowers easily and I know there won't be any capsizing even singlehanded. That's it in my avatar pic.