About twist and differences in design for uni vs sloop mainsails. To compensate for the "bending" of the airstream created by the jib, one want more twist in the top of a sloop main. However, compare twist in these two pictures from Ullman Sicily, one A-cat and one F-18..



Here are some screenshots of a uni and a sloop mainsail. The differences are not too clear, but visible in the areas outlined.