PHRF allows SL < 42.1' and G < 21.1'. I have a symmetrical off a Morgan 33 (40.2' x 23.2") and an Islander 36 (44.2' x 25.6'), and can fly either one without any troubles. I installed a track, but the eye is usually about 5' - 6' above deck. Since neither was PHRF legal, I claimed the biggest one and take a 6 sec hit.