The manual for the Proprietary Software Systems (Frantz)
Angle of Attack instrument recommends a separate pitot/static system.

ftp://anonymous:none@ftp.angle-of-attack.com/AOA%20Manual.pdf

From page 22 of the manual:
   "The AOA requires pitot/static system inputs to
    operate. The installation of a separate pitot/static
    system would provide more redundancy and is
    recommended."

On the other hand, they provide tees to connect to the existing
pitot/static system. I am installing mine that way. FWIW, I am
aware of the limitations and accept the additional risk of using
a single pitot/static system.

Another acceptable risk is that a failure in the AoA tubing or connectors
will also render the ASI in accurate or inoperative.

If you're not familiar with how the Frantz AoA system works, start with
"How it Works" on pages 7-10.

- bob mackey
  flying a 235
  building a 320
  103MD -at- pure-flight.com
  [use this email address - the one at the top is spam bait]