Got a session yesterday on the foils, was blowing 15 - 23 knots so I rigged up my 7m sail and used the 550cm and 255cm foils and the short 75cm fuselage. I should have used a smaller sail, but that was what I had. It was a very difficult session, with struggling to sheet in properly the trim was tricky meaning I was up and down a lot. It was really exhausting so after about 25 mins I went in to change over.
Just to learn a bit I fitted the same foils onto the 115cm fuselage and went back out. It was a massive difference, now I could just track along and in the gusts just load the thing up and use the power. Was much easier to bear off and get speed, or just rail the board over and truck the board upwind. Annoyingly the GPS didn't capture the data so no idea on angles and speeds.
My feeling is the small fuselage seems to work fine on the small sails or when powered up correctly for a newbie foiler. You for sure can feel the flex/twist in the mast at times and makes you wonder if at some point a new style of box mast will come out in the future. If the mast was deeper at the mount with longer mount, then feathered down to the foil.
My take so far is if you are a slalom sailor who uses 6 - 9m sails typically in lighter summer breezes then the Starboard Race carbon is the one to go for. Learning is so quick, don't think there is any need to spend money on "learner" stuff if you are competent sailor. I was out with my moth buddy and it is certainly looking interesting. Even though I'm struggling for tail width on my old free formula I was able to hold him upwind and at times it was putting on ground, more so in the gusts when the foils would lift up a bit and I'd crank harder and really rail it in and get more height and speed. I'm still using a non cambered 8m sail, so will be interesting when I use my Neil Pryde RSS sails!

Need to get a modern board, but that will be a year away so hope the old girl can hang in there!!