Well, I think I figured out the problem. I'm a little embarrassed to post it, but one must share stupidity as well as intelligence.
I went home last night and opened the top of the dryer to check the gaskets as discussed. They are somewhat worn but not to the point of failure. I went over the path the air goes, starting at the heater housing. As you know, the intake port on the frame and exhaust port of the drum have little holes to let the air pass.
I knew the intake was clear because I had cleaned it. Hmmm... the exhaust port is inside the drum. I bent over, and to the port was stuck a couple of dryer sheets, covering it about 90%.
I removed it but I can't test and verify because I have to wait for the new thermal cutoff I ordered to arrive next week.
I swear I had checked that while looking for the problem, but apparently not. Oh well, if the dryer works ok now I'll have a refurbished dryer to use.
And no more goddam dryer sheets for me.
I'll post test results next week. Thanks for the help fellas.