I would love to do this as we don't even use the cabinet under our TV.
Is the 28.5" the total width? Could you provide the dimensions?
I just measured my opening and depth, its 27" high, x 32" wide x 8.5" deep.
Trailer back in Side yard were slide can only go out half way so tough to measure. But front dimensions are 28 1/2 x 21 x 3/4. I think box on back of unit was about 5 inches deep. I had to clean up some wiring and plumbing and relocate sub woofer. I also move 12 volt power center and made it so Dish box goes behind TV so lower cabinet can be closed when Fireplace is putting out heat.