It Appears To Be Fixed!
My hands (even though I wore gloves) and forearms are a little itchy, but I found the problem.
I had to deal with some asbestos, but did so outside and wore a mask. The repair I had to make didn't require doing anything to the asbestos sheet that would create dust. There was a break in the heating wire. My trusty 1950 Electrical Appliance Repair text book advised that if an element has a break, the whole thing should be replaced. I suppose a replacement "heat sheet" for a modern HB or Nesco roaster could be retrofitted, but I decided to mend the break by twisting the wires together. It may not last very long, but I don't intend to put this roaster to daily use.
The result is that it heats more evenly now, although the hot spot is still there at right rear by the power supply, and the mended spot diagonal from it warms up the slowest, but now at least the entire bottom surface is heating. I'm thinking this is just the nature of the circuitry, but it's possible the mended area isn't as efficient as it should be. I'll have to try it out and see how it does. It may only be an issue during pre-heat and not once it hits the set temperature.
Geez, that fiberglass is really a mess to deal with. If I have to remove the surround again in the future, I think I'll use a length of foil tape to keep the fiberglass under control.
Now it's time to shine it up and bring it inside. Yay!
So Paul, is there supposed to be any white paint on the front control panel trim piece?