what exactly is so great about getting harsh instruction from a guy with the body of a professional acrobat?
nothing that I can think of. I got one free trainer session with my gym membership; didn't do much for me - though maybe I should go back for one every few years for new ideas. I quit karate because the higher level classes taught by certain black belts got a little too jock-ish reminding me of all the things I don't like about football.
On the other hand, I do better with some leading and encouragement to do more. I like Z's style pretty well. :-)