Welcome to the sailing forum that beats all other sailing forums. You fell into $#!t and ended getting up smelling like roses by joining SBO.
I don't have a lot of sail buying experiences and others will be along shortly who are experts in the process and in your boat. My experience is that you are going to have to follow that guide and take those measurements because the sail loft would be making some expensive assumptions to assume that everything matches designed factory specs. Different roller furlers have different lengths of swivel and height of drum. Not every mast comes exactly the same way from the factory. On my boat, for example, the step position on deck can vary as much as 6 inches between builds. Then there is rake. This can be sailor's choice. Besides the possibility of a custom modification to rigging by previous owners, all this means it is best to custom measure.
If there are specific questions about how to measure the luff or the foot or where you want the clew to fall, let us know what kind of sailing you do. Race, cruise, weekend, day sail, lake, bay or ocean sailing can all have an effect on these questions.
If you have pictures to go along with these specific questions, all the easier to help you.
Nice boat, by the way. I hope you work this out with little trouble and get back sailing soon. Sorry I'm not more help. I'm just the first to answer.
-Will (Dragonfly)
