Axiom Home Page Forums General Discussion Advice from Axiom Owners Where to place additional subs?

This is kind of a crazy question, but has anyone mounted a sub up on a wall, near the ceiling? Of course you would have to have a sturdy shelf or chain/rope suspending it to the 2x6's.

The reason I ask is because if I get a second sub and place it on the rear wall directly opposite my front sub according to the Harmon White Paper, it would be where the walkout door is, however, I have plenty of room above the door since we have 9ft ceilings. It might be interesting how well it works.