Bruin,
That is a beautiful, but very tough room for a HT.
Are there any other rooms in the home which might be better suited to a HT?
- Less reflective odd angle surfaces, less windows/high light levels, less openings to rest of home, etc.
IMHO the side surrounds being elevated on the fireplace mantle is not the major concern here.
- The seats appear to be set too far back from the screen and L/C/R speakers. I would suggest trying a closer arrangement in relation to both screen size and front speaker spacing. As a ROT, use about 1.4 times the L-R speaker side to side distance as the distance from the front speakers to the main listening point (MLP).
Cheers,
XEagleDriver