Only if he cares how the sail turns out! If you are trying to determine what is important to order a new sail with specific attributes, then you should discuss this with the sailmaker you are interested in using. Especially helpful is to send him your current sail that you want to replace along with your input about that sail - what you like and dislike. Not only will that help him produce a better sail, he may be able to recut your old one (if it has life left in it) to be more like you want so that you will have a nicer practice / fun sail to use. Since this is Rick's site, I'm throwing him a bone. Get his book(s) and read about his 3 Ws method of determining the basic sail shape you want in varying conditions. Ideally, you have a mast with enough movement to allow you to shape the sail to the conditions. If it works well, you just need to be able to recreate that shape when needed. If not, then try to notice what shapes are doing well and see if you can recreate those. Sometimes seemingly minor adjustments, like batten stiffness, can make big differences. If you cannot create a fast shape compared to others on a given day, make sure you discuss it with THEM. Ask them to describe what they were doing, and to show you, and then see if you can get your sail to a similar shape and performance. When it becomes clear that a shape is too full, for example, to be fast in heavy air, and you race a lot in heavy air, then you can let your sailmaker know that you need a flatter main, and ideally, suggest how much flatter. There is a lot to learn about sail shape and that is just a little of what helps keep it interesting after 35 years of racing!