Departure from optimum may exacerbate the problem.
I note the OP mentioning moving to greater diameter
If there is a hump, the metal is stretched. Beating it down can at best make it pop the other way.
Many people have chimed in on this thread. I appreciate all of the input. Some have sent me detailed PM's which are very thoughtful and appreciated. Sorry I have not responded to them individually.
At this point I am not having any problems. I think I was having a combination of issues. The easels are slightly bowed, but very slightly and not enough to make a difference normally . Also, I think the the 4x5 negative in the carrier was not popped but bowed. I use a Negaflat carrier which is excellent for flatness but I had the negative sitting in the carrier at least overnight without re-setting it so I think it sagged a little. Also, I had aligned my lens with the Beseler tool but then I ponied up and bought the Verslab which is much more precise. I still don't have it perfectly aligned but very close. And I stopped my lens down a little for good measure as well as for base exposure times in the 20-30 second range which I like.
So the combination of adjusting the negative in the negaflat, aligning the negative and lens with the Versalab, and using f11-16 on the lens has done the trick, at least up to 16x20 prints which is as large as I plan to go (except for the occasional 20x24 of course).
So thanks again for all of the ideas and thoughtfulness of replies.