I don't disagree that you need several, what it/they say and which doc says it is more important. Your current doc treating your main disabling condition is the most important. They shouldn't widely vary regardless, if they do than they're not accurate.

It's not a bad idea to have testing done that shows more than a doc's random guessing as well. This is often performed by a physical therapist. I can't write or use my dominant hand without swelling occurring within a few minutes for example. With a water displacement test it was easy to prove my complaints are not just subjective.