RE: For Ian RE C3
Likely it's Z1 @ 27/31/33, bcos X1/X2 really only ever go to 24-25cm.
These are two different fin types, the X1/X2 being the heavily raked speed specific and the Z1 Zulu being the super slalom. Z1 27 will be very good for speed on S90 when well powered and broad on flat water (definitely a 40kt combo), & for marginal megaspeed (esp with 107kg) the 31 would/could also be a good option for S90 in less than fully lit speed.
As you likely know, those fins are a bit like gold, don't grow on trees, so as long as they are in good condition, should be a very good catch.
Neither the Z1 27 nor 31 would be "redundant" with new iS's , either..
Cheers ~ Ian
PS: we're taking bets on whose fins these are (were).