The Capricorn wingmast has a circumference of 0.365 mm (I have a section cut-off at home !) on a 9.15 mtr tall F18 mast this makes a total mast area (as defined in the F18 class rules) of 1.669875 or rounded off to 1.670 sq. mtr. The Tiger mast area (0.330 mtr circumference) is 1.51 sq. mtr.

If the Infusion mast has the same dimensions as the Capricorn superwing (very likely) then the cloth part of the mast+sail combo (= actual mainsail size) may only be 17.0 - 1.67 = 15.33 sq. mtr.

Anything over that will be ILLEGAL under F18 class rules.

If 16.6 is no typo then somebody is going to get very busy with a pair of sissors.

And 16.6 sq. mtr may well be enough grounds to start analysing whether this is indeed a simple cutting mistake. 1.3 sq.mtr difference is like adding two feet of cloth at the foot of the sail or halve a foot at the leech. You don't easily achieve that by an "oops" mistake.

Wouter