RE: Board for my girlfriend
Hi Andrews, the Solo looks OK.
Be sure to ge the 400 cm X6 mast (or another 400 cm IMCS 19 Std. Dia Mast that's even lighter than the 55% Carbon X6).
As far as a arger sail, you have to be careful not to get too much gap between your sails or you will have an "unbridgeable hole" where the larger size is too big and your next smaller size isn't large enough.
6.5-8.0m2 is stretching things almost too much. If you can afford it, a 5.0/6.5/7.5/8.5-9.0 quiver would be great, but you also need to factor in what the min. windspeed to plane is for your larger board.
Your 190 ltr GO can easily handle a 9.5-10.5 to get the max. early planing (with a larger fin). but the smaller Carve can only handle up to around 8.5 m2.
Hope this helps,