The jumpers should be tight enough to support the upper section of mast so that it is straight when the backstay is slack. but loose enough to allow the top of the mast to move aft just enough to get a smooth and uniform bend from the mast head to the step, when the backstay is set up hard. The amount of bend you set in, is a function of the draft in the mainsail and should flatten the main only enough to take a portion of the draft out, not all of it. Your mast partners should hold the mast centerline but allow it to move forward at the deck to produce that smooth bend all the way to the step. Uppers should be set up tight initially because they will ease off as you induce bend. Lower tension is a matter of choice. Some like the aft lowers loose to allow the mast to kick forward a little when under chute with backstay off. Others like the fwd and aft lowers equally tight to to hold the center of the mast fixed. I like the former in heavier air and the latter in light,
Good luck.
Joe S
