ORIGINAL: waagbuck

I've experienced the curving straight line effect and redone quite a few pieces to fix it. Try using a wet paper towel along the straight edge of the ultracote trim as you iron it down. This keeps the edge cool and less likely to shrink. Also, one advantage of ultracote is that you can heat it up again and pull it off if you don't like your first try. Monokote doesn't allow that.