Bg,although prestretching is good,that really isn't the big secret to quality string building.Serving correctly is the secret.Making sure the serving is served in the same direction of the twist in the string and very tight will keep a peep from rotating more than just prestretching.Prestretching along with proper serving and now you have a string that just won't hardlymove untill it breaks.[

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I had a d-75 string made for a single cam bowthat wasn't prestretched but was put on a shooting machine for 3 days after it was built and I don't think I ever had to move the peep.I have had a few others that were made out of various materials,all high quality, that were not stretched on the machine that needed a very minor adjustment after about 30 shots.But never needed to be moved again.
utmstudent will benefit from somehigh quality strings but they would cost as much as the bow is probably worth[&:].Twisting the string like you stated may help but the string definately needs some shots to help settle the serving.After that if the peep is still rotating, a d-loop might help but it may neccisary to get a tube style peep.[:'(]