I recently both a GO 151 my experience is that the center fin does not work well for a small sail 1,5 m the board keeps getting aside instead of forward. For a bigger sail its oke I use sails from 9.0 till 5.0 depending on the wind. If you go for a freerace sail with 2/3 cambers you will have a good combo to go fast depending on your skills and also use the board for your kids. For the Go from 21 knots with chop the board feels like a skippy bal you bump a lot.
I also tried an iSonic 133 these type of boards have a better accelaration and can better handle the chop. You would be wise to test such a board first.