Thanks for the detailed answer, which unfortunately leaves me uncomfort...
Compare these two cases:
1-20kts wind, 2-28kts wind (I encounter it a lot recently here). Same board AHD 265 90l, same sail NP ZEN 4.9 (no problem holding it and fly at 28kts!!), same fin 28cm slalom, same me 65kgs, 166cm high. Assuming I surf at the SWEET SPOT in case 1, what should I do in case 2? FWD or BCKWRD or none? or still no straight answer....
Thanks for the best answer I got out of all forums!!