I have no idea what the sailmaker was doing..

My guess is... He interpreted the rules to mean Sail Material must be legal... which it was..

He could have thought reinforcing tape is not regulated as sail material.

So, I would judge "mistake"... not cheating... Solution: fix mistake and re measure.

That is what the jury did Mistake... cary on.. .... NOW the class has some issues here that are not transparently resolved.

(I will be thunderstruck if you checked out the reinforcing tapes on your sail were on the proper list...)