Hi Stephane

I have (had at some point) all three boards you're contemplating: 70, 75 and 80. I just came back from Almanarre for the IFCA Slalom Worlds Y/M where I used the 75 in most races.

Of those 3 boards the 75 is the perfect board for 8.4 for me - but I'm only 73kg, so more than 20kg lighter than you. The 75 has the speed of the 70, plenty of control and low-end planning capacity to get/keep going in the lighter stuff. In terms of 'feeling' I felt that the 75 is closer to the 70 than to the 80 - but that's just a feeling.

This is a tough one. To "really fly" in 12 knots with 8.4 at your weight I think you would need the 80. It has a lot of control. I sailed it quite a lot last year with 8.4 on the North Sea, and in the wind range of the 8.4 I was never caught out out of control. However, at my weight I'm just more efficient around a race course on the 75 than on the 80. And at 18 knots I guess you would be more comfortable on the 75 than on the 80, maybe just slightly. (Of course, it also depends of your skills etc.) So maybe two things to consider:
- in the 12 to 18knot range, where will you most likely be: at the lower/mid end, or in the mid/higher end?
- the switch down to 7.0/94liter seems a bit easier from the 75 than from the 80, but again it all depends of skill too.

All in all, if you liked the 70, maybe the 75 is the way to go. Drop me an email, maybe we can arrange for you to try my board.

cheers

c