Was putting the side panels back on after replacing some of the louvers that had come apart. I noticed how the bad louvers were warped, and figured it must be from the excessive heat they're subjected to.
As I thought about it, I don't remember ever wanting to open them, and how even when closed the heat coming through them is uncomfortable, so I decided to block them. I put a thin piece of insulation over them, with a dab of silicone at each corner to hold them in place.
If anyone wants a bit of this insulation to do this, let me know and we'll work something out.