I just bought the new Jamis Aurora (59, 06 edition). Great bike--when I was looking at it this mornign before a ride, I noticed that the top tube angles slightly (very slightly) downwoard from the head tube to the seat tube. I moved it around my apt. to be sure it wasn't the flooring and noticed it again. Am I seeing something that's not there, is it designed to be angled or is it a man. defect? If it is designed that way, to what ends? Thanks in advance for any insight.