I have about 10 of them Killebrew is not one of them. Most I have come across have warping to the base. I have been told that there is a technique to correct that without damaging it. Unfortunately I cannot remember the details. I have found the owner of this website
http://www.hartlands.com/ to be very helpful and knowledgeable. If you call him be prepared for a long discussion as he is passionate about Hartlands.