I have used poly, 80/20 and 50/50. I for my personal ones like the 50/50. I long arm a lot of charity quilts and they use the poly. The very first one I did I started out with a lot of bearding on the back 1st row, put in a new needle and since always check the needle and haven't had any more problems with it on any batts. Am planning on doing one with Deam wool just to check it out.