PM is subject to the same ergonomic and physiological limitations as any other person on the flight deck. I also know that the PM is required to remain in the control seat during normal and non-normal operations. If you are required to stamp your feet on the stab trim you have to be:
a) out of the control seat and
b) flying in an aircraft that should never have been certified if that is what is required to maintain control
Clearly every regulatory agency should have contacted you first before grounding the aircraft and require Boeing to spend the last two year fixing, (according to you), a sound design that only hit the headlines because of incompetence.