I usually have it at about a 45 degree angle.I'm guessing you don't like the neck in as extreme a vertical position as I do most of the time. I have always preferred the neck pointing at the ceiling, almost like an upright. It made learning to play upright a whole lot easier, since the ergos were similar to what I already do most of the time.
One of the great things about a Thunderbird is that you can wave the neck around for a lot of reasons. For me, it's partially ergonomics, partially just putting on a show.