I understand how one would see this as an air trap, but the Amtrol instructions specify only vertical (not horizontal). I am willing to bet that any trapped air will be resorbed. Given the pressure, if one were to take the time and go through the chemistry calculations, I expect trapped air is not a problem.
Now, there is a shutoff installed directly below the tank. This was put there purposely for easy removal. I am not concerned about the weight under failure.
There was an ulterior motive too. I did not want my kids wrenching on the tank. They can't reach it where it is now.