I still donīt get the point of the discussion
I just have to ask again why does it matters so much? All of you guys writing to this thread have more than one board, rigth? And as you bought your first board you discovered what is the favourite sailsize for the particular type and volume...and if you want to go down or up you take a look at the range given by SB and you go for a board having the same sail range (relativly)...so what for is this forum...and the reply just to know why, or to help people without any experience....this is not helping, at least I think so.
There was already mentioned that all other things are important.
Everyone who buys a new board gos and try in the conditions what it was made for and if he realize that the sailsize is not OK, take another one. And if there is not other one...only thing that left is to try harded and donīt give up to learn how to use it with the sails you have.
And I have to add one personal thing...there are days that I go with the biggest sail for my Aero 117 or smallest sail (or even smaller) for ST137 and I like it. And there are days when I do opposite and it is better that way. It depends strongly on spot, waves, chop size and orientation, if the wind is gusty or not etc.
I am not lightweight (in neo...95kg). And observed that it very much depends on conditions than on a sailsize.