I tried my new polytarp MiniCup sails that I had edge shaped. One was
shaped according to the polysail directions with more "body" than the
other. The more "shapely" sail was really bad. The less shapely sail
had a problem at the leech where it curved radically to windward so the
air cannot flow over it too well. I tried to tighten it to get this
curve out with little success. It seems that lateen sails should be
cut with NO body and maybe even negative shape. I am not sure of my
next step but will involve some experiments.