Angular Reflective Screen and Shelf Mounting

I've been battling this for a few weeks now. According to Elite's website, in your case with an angular reflective screen the ideal placement
for the PJ would be 2 feet above center if viewing is 2 feet below center.
I have been testing angular reflective materials for my setup. 96" screen, 13 ft throw ceiling mounted, viewing from 12 ft.
All material I have tested (Elite Airbright 3d, 5d, Powergain) are fine in the center but the image on the right side of the screen is almost
non-existent if viewed from a point even with the left edge of the screen. Basically worthless sitting on a full size sofa 11 feet away.
All the viewing angle specs deal with the light reflected from the center of the screen and do not address the issue that the limit has been exceeded
by the time you look at the edge of the screen.
td