Those panels will melt. Some years ago, I was using my backpack blower and for a moment I had to back up against my C-30 passenger side door (window was open) as I was blowing leaves. I quickly smelled plastic, turned around and saw a 2" diameter area on the top of the door panel that had begun to melt!
I finally did a refurb job on the panels and finished 2 days ago. They turned out nice. Yours did, too. I liked your well thought out and detailed, clear explanation of your process to prep and coat the top section of your panel. Mine had similar scratches but also included the unique "backpack artistry" to hide. Copying a process I saw someone else use for refurbing dashboards, I sprayed a few a few light coats of Rustoleum clear undercoater on the top section only and protected the rest of the panel by taping at the contours so any spray line could be blended and removed easily. The Rustoleum covered the damage and left a very light texture but with a slight sharpness I didn't want. That smoothed out nicely when I coated the panels, fortunately.
Here's a side note I'd like to mention for everybody about a great old product still available if you hunt for it. It's called a Preval sprayer.
Refillable DIY and Pro paint spray systems. Spray any liquid for professional results. Order Now or call to become a distributor 877-753-0021
preval.com
I have no connection with the product or company but I recommend them because they work great. I found out about them and first used one around 35 years ago. Home Depot stocks them and they were fool proof for painting my door panels.