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Let's see 6 m/s to 9 m/s is 11.66 knots to 17.5 knots.
OK, so now we have the wind speed and the sailor weight (83 Kg. = 182.9 lbs.).
Have you ever sailed a board without a centerboard/daggerboard in fully planing mode (i.e.
the front 2/3 of the board is out of the water and the board is planing on the remaining 1/3 (from the
front footstraps in the rear position to the tail of the board)?
Until the wind gets up to around 14 knots, I do not think you will be planing on a 7.0 m2 sail on the GO 144.
If you know how to make a true shortboard (i.e. no centeboard/daggerboard/center fin.... just the rear fin)
stay upwind already, then you will take to the GO 144 like a duck to water.
If you have no experience on a shortboard, we can help you with that.
It won't be the easiest of transitions, but you can do it, lots of us have done it in the past!
You will soon be wanting a larger sail (I'd suggest getting a 7.5 m2 rather than the 7.0 m2) so you can plane more when the winds are < 15 knots.
You are pretty much on the right track, if all of the parameters you have given us are there.
Less wind, and the GO 144 might not perform as well as a Rio M.
If you have the stated 6-9 m/s most of the time, then you will be quite happy with a 7.5 m2
free race sail (2 cams or no cam).
Hope this helps,