Nice picture! The measuring marks on the edges are a nice touch.
I agree that with the Panny 900, you'll have no screen door effect, even for the front row viewers. I am in a HT with very similar dimensions to yours, with two rows, and I get no SDE from my Panny 900.
I would probably move the QS8s about 3 feet back to give better rear effect for the second row viewers. The benefit to them will be greater than the loss to the front row by such a change.
BTW, where will you likely sit when it's just you and the wife? If it's on the sofa, then definitely move the QS8s back.
Good luck!
