I have been trying to order a new main over the iternet (Far East sails) for my 1979 C-30 standard rig. Measureing the luff (36'2") and foot (11'3")was easy. The leech is the problem. Should the boom be placed at 90 degrees visually from the mast? I measured the leech with a slack topping lift and got 38'5". With these measurements the sail maker told me the tack angle would be 93degrees which I have been told wasn't ideal. I remeasured the sail with the boom more or less at 90 degrees and came up with a leech of 37'8" which doesn't seem to me to bring my tack angle to the 86-87 degree reccomendation. Has anyone else had similiar problems, or does anyone know what the measurements of the main should be? Thanks