Great job. Looks wonderful. I would definitely get a cover. Maybe valves are not quite synchronized and one side is getting more gas than the other. Do a toast test. As long as you know where the hot spots are you can compensate or use to your advantage.
Thanks for all of your kind words. Even with some of the frustrations, it was a fun project and I'm happy with the results.
I will investigate the valves to see if there is a way to adjust them. I had a couple of extra that I can play around with, or maybe just swap them in to see if it makes a difference. But it's not that big of a deal (yet).