Well, it's been awhile since I've done needle turn. However, I used to taper trim to the points being careful to leave enough fabric to turn under. If all else failed, I used a toothpick to place a very small drop of water soluble glue to tack it down until I could get it sewn down. There are tons of books, tutorials etc. that deal it the problem. The only other thing I can think of that might contribute to the problem is that the thread is being pulled a bit too tight in this area. I'm sure you will get lots of suggestions from those who are far more up to date than I on this technique. The quilt sound exciting. Please post.