I'm no racer, or expert on rigging, but always try to rig as small as the conditions allow.
I've been surprised at how small one can rig to foil in high winds.
For years riding on the fin I thought 4.5 was a small sail. Then I realized it's quite a big sail for windfoiling.
My favorite sail is now a 3.3 Severne S-1 and it's a game changer - such a nice rig for 18+Kn.
I've enjoyed my kids 3.0 XS-1 in 20Kn too. Imagine a 300 mast & 140 boom

I don't find much need for my 4.5 now as I often step down from a 5.0 Gator to the 3.3 as the wind fills in.