I don't know that I can add much more to the issue unless you have another question.
Regarding the iS 111 and an 8.6 sail, I have a Maui Sails TR3 8.4 with an HPL carbon formula boom (very heavy). The whole rig is very heavy and not my favorite. I went out on this two days ago in building, but variable winds as a front came through, It was fine for a short time until the wind hit 18 knots, then it was a struggle for me. In the holes (off plane), the rig is not great at slogging. I weigh 78kg. I am also 65 years old, so I have a little more difficulty hanging on to big rigs in strong winds. Bigger stronger guys will do fine with an 8.4-6 on the iS111. When the winds are steady, I do fine with my 8.4, but in the holes and gusts, it's not fun.
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.