Hwy1North said..
The Kd method is great for finding your boards center of balance with foil lift. That way the board is neither weighted forward nor aft on foil, and you can then fine tune for what works. Foils lift the same whether in the rear or full forward, the difference is where you need to stand to be balanced. Full forward on a long windwing board will make the board feel shorter on foil and thus smoother, but on a shorter board or while using foot straps, it's just a matter of finding the correct balance. Ideally, winging, you want your slog position to be very close to your flying position. This hopefully is the same point as the Kd method. The newer high aspect foils require less "dolphin" and more initial speed, so a board with a wide tail, no chine, and hard edges will make planing speed easier and the less wetted area may come in to play at lift off, but for a Helium and your long board and no straps, I'd keep it pretty far forward, but not as forward as say an Armstrong and that will start a whole new thread on mast to foil spacing and effect on lift while turning...
+1!!
Manufacturers tried to simplify things by putting those +lift and -lift at the front and back of the foilboxes.Which is a well meant lie that kinda works but really does not and has everyone thoroughly confused :).
A given foil only gives more lift if you increase one or both of the following:
-Speed
-Angle of Attack
That's it.
(Getting nitpicky a bigger stab at a bigger downangle creates a downforce that substracts overall lift.But it is marginal.
The stab main effect is in foil drag, balance and how it reacts to speed changes.)