Thanks davide for your thoughts. Your strategy is now much clearer, and sounds very well based.
With respect to my old ML board, it's a bit of an ancient relic, although a pretty good one overall. It's a 9'4" and only 23.5" wide. My thought with a new board would more like 8' and maybe 70cm wide at most, as I don't want to go any bigger than an 8.3 sail. Still though, dimensional details are sketchy right now, and I've always been one to let Mike do what he feels best.
Getting back to your board dilemma, I'm thinking in parallel with most recommendations here that the iS111 is your pick, as the newer designs really perform very well with large sails. My 100 liter ML works fantastically with a 7.1, so I'm thinking that you're right in there with room to spare your 7.3 and the iS111. By the way, I'm about your weight at 75kg.
Lastly, I'd bury the JP idea. Although I really can't comment on the performance of the JP SS118 you're considering, I bought a JP in 2000 and it was a total dog, so I'm somewhat prejudiced. Also, at least in my opinion, the iS111 is, without a doubt, a much better looking board.