I like seeing my engine through the side covers and so I removed the vented panels. The problem is the massive amount of heat that blows on my feet and legs during the summer.
I found 11" x 14" clear Lexan sheets at Home Depot for $3.49. They are the perfect size to make clear side panels. I made the panels and installed them yesterday. They work!
I would show you pictures, but, you can't see the clear panels in a photo! Maybe they will get dirty . . .