I have a tendency to agree with speedoo. I know that kevlar is stronger but always believed the fibers were sensitive to shaking as in a flogging sail, and can be damaged by hard creasing, such as happens when you douse shorthanded, and flake or furl mains, or gather and stuff head-sails. If everything is on a furler
then some of these problems are diminished.
Most cruisers only use dacron sails because they give reasonable life for reasonable cost and can be adjusted, and readily repaired over their life. Storm sails and any others you might not expect to have tweaked during the course of their life, can be glued on the seams before stitching. Leather on the corners is a plus. You also have to specify the number of reefs
you want and maybe the amount of reinforcing.
If you want a cruising main to last you will also have some Baggy-wrinkles on your shrouds to minimize chafe when sailing downwind (the cruisers favorite direction). Furling
head-sails should have ample UV protection sewn into the leach and assemetrical (sp) spinnakers should have a sock also to protect from UV. Full battens save a lot of wear on a main and give much better sail shape. Unfortunately they don't work
to well with furlers. You may however want to specify how you want to have the battens secured at the leach, and what kind of batcars you want at the luff.
Sail cloth comes in many different thread counts, and stretch in the woof, the warp, and the bias. You can get good quality material from most reputable sailmakers. Hood originally made his reputation by making his own cloth but it was narrower than standard widths because he had narrow looms.
Most cruising sailors give only general directions to sailmakers because most reputable sailmakers will give you a good product
Most people would get themselves in a lot of trouble believing they know more than the sailmaker. It would be far better to sit down with your sailmaker and discuss these variables rather than prepare specs before hand. Then you could mutually agree on what you should expect to get.