RE: Earliest planing with 8.5 m2
Again with my 65 kg, by using an old '98 race board of 309 x 70 cm x 170 L, I need 10 knots of wind with same 8.2 race sail and same 48 cm race fin to be able to start and sustain the planing. For my light weight, a long board doesn't appear to play an essential role in early planing, except perhaps it's easier in the beginning to find out and adjust for the correct nose/tail pitch of the hull with a long than with a short board (see the enhanced lenght of the Apollo versus that of F161). Volume doesn't play a big role either (103-170 L) but width does (70/77/80/95 cm versus 63 cm). For a heavier body weight such as your 97 kg, I'm sure this is a completely different story, however...!
As for cammed race sail versus no cam sail, I can't really comment because I don't have both with the same surface. However, my experience taught me that the more deep the draft is, the more powerful a sail can be in the lowest range and cams do help a lot to pre-shape this deep draft in low wind range. I need 10 knots with a race RS2 8.2 sail but need 12 knots with a no cam freeride Jet 6.9 sail; or, I need 15 knots with a either a race RS1 6.6 sail or a wave NR 6.2 sail (all with adjustable on-the-fly outhaul).