Generally, I foil on the slingshot 115 with infinity 76 in B position with a 3.7m and 4.7m and have everything pretty dialed (mast track forward, straps forward and foil track all the way forward) for how I liked to ride (in fact, it is totally fraking awesome). In particular this set up gave me a more heavy front foot, which I like. These settings seem to work well for the infinity 65 too, but I ride it less than the 76.
Recently, with the lighter winds I have been riding 115 with a 5.7 and the infinity 84 in C position. But with the same settings (mast track, foil track) it needed way too much pressure on the rear foot. It got a little better when I moved the mast track back. To me the center of lift between the 76 in B position and the 84 in C position look similar so I was surprised I needed much more back foot pressure. Perhaps this need for much more back foot is a function of being under powered?
Do you guys feel the need to adjust positioning (eg mast track, straps, foil track) when using larger sails and/or bigger wings?
PS: As an experiment, I switched to the large rear stabilizer mid session and it needed even more back foot pressure, especially to pop the board onto the foil initially. It was slower than the 84/small stabilizer but did seem to foil through the lulls better.
In my experience the wind strength (same wing) makes a major difference to the balance of the board (foot pressure fore or aft). The higher the wind the more front foot pressure I need to apply and to help me do this I either need to move the foil's mast forward over the wing (position A) or the mast forward in the mast track (or place my front foot in front of the foot strap).
The Infinity 76 becomes unmanageable for me in 15 to 20 knots without making some major changes to my setup. What works fine in 8 to 12 knots does not in 15 to 20! There's just so much more lift with a big wing once the wind pick up.
