Now that I've read thru your straightening instructions, I've got a couple of questions: After you wet the yarn and towel it dry, what have you used for a weight to pull it down??? A flashlight?? A 2 pound weight?? Not sure what "too heavy" would be.
Do you have any pictures of what this would look like? What do you hang the yarn bundle on?
I hang the hank of yarn on a plastic hanger, and add just enough weight to make it straight. Depends on the yarn, and how thick the hank is. One time, I put a small hammer as a weight. Another time, I used a bottle of glass cleaner. You'll be able to tell.