I have a Brother PC-420PRW, and for the most part i really love this machine. but, there is something that irks me...why is it, that the bottom thread never looks as neat as the top? i mean, if this is normal, im ok with it, but i tried everything. i made sure the needle/thread combo is right. it is not terribly bad, but it always seems like it's never as nice as the top. maybe i'm not setting something right...anyone else have this problem who has this particular machine?