Sounds to me like you are getting your tail material all bunched up on one side of the hook. After you get your thread started and begin to tie in your tail material you need to make sure that it is even all around or at least on both sides of the hook when you wrap it in. Make sure it looks pretty uniform and round before you wrap your body material. The thicker and fuller your body material is - the more it will hide. If you use a chenille it will usually make your body look nice and round. Hope this helps you some!