The TV still goes into a steady vertical roll after running for about half an hour. Acting on advice from an experienced TV repairman, I used a can of spray coolant to isolate the component that was causing the roll after heating up. It was a capacitor C54 in the vertical section. Funny thing is, I had already replaced C55 and C56, which lie on either side of C54 on the chassis. In the course of recapping the whole set, I eventually would have solved the mystery by brute force, but it was a lot more fun to successfully diagnose the problem and see it go away.
Freeze spray is very handy for diagnosing problems due to overheating.
I have used it in a couple of other repair jobs since then. Between cooling and heating a component, you should be able to tell pretty quickly whether it is changing value. The TV is in pretty good working condition now. All but one or two of the old paper capacitors have been replaced. I still intend to investigate the power supply, but we're moving to new house this summer, so the project may have to wait.