Yup. Cut them at the angle you need. Should be pretty easy to do. The 2x8 idea may work too, but if this thing is as heavy as you say it is (I am a "capable" guy, and I can manhandle about 120 pounds "accurately", I can lift more than that, but sliding a TV into a hole about 3.5-4 feet off of the ground takes more that just lifting, I figured that if it is taking 2 guys to move this thing, it must weigh more than that) then the vertical bracing is a must or the shelf will bow or worse rip off and drop.
Piece of mind is for $12 plus some cutting. You'd spend about that much on the 2x8 and mounting materials (not sure how the 2x8 is attached to add any support, so I am only guessing on its capabilities).
Or just rig the whole thing up with my "design" and Veinman's 2x8 pieces and the thing won't ever move.
