The original question pertained to upwind on a formula board. Bel had it correct, but as post #11 said, speed is the key. However, railing a formula board more than 10-20 degrees is counter productive. The idea is to keep it as flat as you can, but it will rail up some anyway.
Upwind takes SHORT harness lines and a flat sail - downwind takes LONG harness lines and a full sail. All formula racers have adjustable harness lines so they can lengthen the lines as they round the upwind mark and shorten the lines as they head back upwind. Outhaul gets the same adjustments at the marks - flat upwind and full downwind.
Almost all your weight on the back leg going upwind and it should be straight. However, both legs may need to bend if you are going over large chop to keep the board down on the water. If you get any air, it can spell disaster. You curl you toes up in the front strap just to keep your foot from coming out, no need to lift anything.
Formula 160; iSonic 111; HiFly Move 105; Tiga 263; '85 Mistral Superlight.
Maui Sails TR 11.0; 9.2; 8.4; 7.6; 6.6; Maui Sails Switch 6.0; 5.2; Maui Sails Global 4.5; 4.0.