Sorry, I can't find my photos. The foil may be an easier install. I used insulated foam board. I believe it is R10 rated. I attached it to the metal studs behind the front closet with self tapping screws (with large washers to prevent busting through the foam) & Grab it chaulk. I also covered each seam (where foam board pieces joined) with foil duct tape. I covered the entire wall cutting to fit at the ceiling & I covered the exterior of the access box (using Grab it) with a thinner foam board that did not exceed the thickness of the box frame. This allows removing the access box with no issues. The interior of the entertainment center cabinets gets very warm on hot days so I plan to copy Fred & Toni's idea using foil there. Regardless of the method you choose, it is beneficial. I left the hanging fiberglass insulation installed at the factory but it has many large gaps & is quite useless (in my opinion).
Wayne & Sheryl
Plus Ollie & Sophie
(they don't know they're dogs)
2011 Ram Laramie 2500 CC 4X4 6.7 Cummins
2015 Columbus 320RS
"Where ever you go, there you are" Buckaroo Banzai