These are basic tips for trimming the J 80 main which will help you establish a go-fast position for your own preferences in trim.
TWIST IS FAST. By twist, we mean that it is necessary to open up the top of the leech and maintain flow over the top of the sail. A good rule of thumb is to trim until the top leech telltale is just stalling and then ease out 2-3″ inches of sheet so that the telltale is flowing again. This is unlike many other one-designs that like to have the top batten parallel to the boom in most conditions. In order to keep the sail powered up and the boat pointing with so much twist, it is necessary to pull the traveler farther to windward than you may expect. Quite often, the boom is 15-20″ above centerline.
As the breeze builds, you need to maintain a balanced helm. Begin by pulling on the backstay to flatten the top of the main. Drop the traveler down in increments of 6″ for every 3 knots of breeze above 10 knots. As you drop the traveler, you need to pull more mainsheet to tighten the leech and maintain pointing ability. In a big breeze, the top of the main is twisted off and the bottom 1/3 of the main is doing most of the work.