Rose, I would try to find out what loft made your original sales, or contact the major lofts to ask if they have dimensions on file. Surely, SOMEONE has already made these sails and has dimensions on file. I know that doesn't ensure that they have fully accurate and correct dimensions--but it is a start, and about 800Eu cheaper than buying
Your best defence against an amusing insurance
company is to check your policy terms, and then call your state insurance commission (if you are in the US) or similar consumer/insurance regulatory agency. Find out what your laws entitle you to, what your contract
binds you to, and then make it clear to the insurer that you will require them to conform to the laws.
Begin every phone
call with asking the party's name and position, and let them know that and their comments will be on the record
. If their manner is unprofessional, ask them who their supervisor is and then politely insist the supervisor be put on the phone
. Don't allow them to play games with you.
Since you don't say where you are, I won't speculate any further on how you can deal with them.