Repeats in Hem Frill

I am in a quandry over how many repeats to do in the hem frill. I have 14 right now. I have read that the Butterfly will stretch like crazy.

If I pull on the lace a bit, the hem measures out to 42 cm. (I think that I am going to make the XS.) Plus, you stretch it when blocking to enable you to see the pattern clearly, correct??

Thanks! Hope everyone is having a good weekend.

Ann Marie