So I have a 7x16 Car Mate that I converted to a poor man's toy hauler. I recently installed a Mach 3 Power Saver and it does a great job but at the races this past weekend in the 90° beating sun, the interior would only cool to 78. It was still plenty comfortable in there but as a little experiment, I backed my trailer up into the shade for the afternoon and the temp dropped to 71 within 30-40 minutes. I currently have zero insulation. I used 2x4's to brace the roof for the weight of the AC so I have enough depth to roll out some fiberglass insulation in the bays and then finish it off with some 1/8 inch luan or something similar. Is there any reason I shouldn't use fiberglass if I have the room? Here is what the roof looks like and below that is a pic of the AC installed. I'm also going to coat the roof in Henry's.