installing cringles for reefing is simple and cheap. but to be done properly you need to request from whom ever will do the following things:
1) the cringles must be good size to passa reef line thru them, I have seen sails with reef cringles so small that limits the size of the reefing line, that has to be thick enough for hand confort.
2) The cringles should be applied over a strip of hard resistance material, that is sewn onto the sail, not just in the sail, this is to spread cringle loading onto a wider surface. (see the strip I talk about in below photo).
3) The cringle area should creata a patch, formed by triangular sections of sail cloth, all sewn in the sai, with the wider part of the triangle where the cringle is. (see photo bellow)
4) A larger rectangular patch should be sewn directly onto the sail to beef up the area. (see photo bellow)
That is how it should be done, and what you should require from your sail maker...these features I mentioned here no only prevent sail tear and rip, they also make sure you can still trim a reefed sail with out it deforming, which would happen without the all the above items.
do not settle for less. This is a properly done job. If you have any more questions let me know