"Applying tones to hear when it rubs works well."

I do that. I use a function generator on sine and set it to the free air resonance frequency It is easy to see, whatever frequency moves the cone the most. Then I see which way it might have to go to be in the most perfect center. It could be fine without touching it but I push it both ways on both axes to find which way the bent bends. Whichever way I got the most clearance before the voice coil rubs is the direction I "coax" it to before the glue dries.

Once I had to fix one someone else had done. He thought it would require removing the glue and tearing everything out. Nope. I simply bent the frame slightly. Of course this will not work on speakers with cast frames so just be more careful on those.

Actually there is money doing that. I heard of a guy in my state who started doing a few and still worked. In a couple of years he quit his day job to do this full time and makes decent bucks doing it. He can't keep up with the work. I am considering doing it. All you need is a little bit of exposure and a few satisfied customers. And of course I would have a discount for cash... It would tie in nicely with any of my stereo fixing endeavors as well, it would be practically the same customers. And audiophiles go in packs, at least on the internet. Of course some of them will fly cross country to hear another's system, but when your system cost more than a new car you do things like that.