My local loft that made my new headsail designs, cuts, and assembles ALL sails in-house. How do I know? I watched the whole time. They were very thorough in measuring. The owner of the loft even came out and raced one day with me to see how the sail was performing. After the race he recommened a couple of adjustments and then took the sail back and made the changes at no cost to me.
In my opinion your thinking is correct, but you should try having this same conversation with the sailmaker. Give them as much info as you can and ask for their input as much as possible. They are the professionals, and should be able to narrow your options down for you.
Maxum 3200 Miss Adventure
Formerly - Tartan 34C Yawl