SeiserL

Perhaps (for me) the best way to teach/apply the "unbendable arm" is not to focus on the arm (or point of contact/resistance) but to focus on the internal body structure/alignment (that includes the arm) and filling the 6-directions to support the arm/body and "let" it remain straight/extended ...
I used to just visualize a metal bar extended to the hall in front of me and the wall behind me and just let it pass through my arm ...