Hey There… I’ve resolved Tenor issues for myself and students by sitting forward on the chair, using a chair that has no arm rests so that the arms can find their neutral hanging position, and by placing a thumb rest so that the right-hand pinky approaches its holes perfectly perpendicular to the instrument. For most, this means the rest will often place the right thumb exactly opposite the right middle-finger when holding the instrument. The resulting sharper bend now in the wrist hasn’t caused anyone any pain here to date.
Once the problem is considered resolved with a plastic rest, a wood or cork rest can be glued there to create that same hand position. I mention gluing the rest as you may find the plastic one will slide upward from pressure on the thumb rest to get that hand low enough down the instrument to position the pinky. — k —