Re: If you disagree with your instructor's explanations...
Interestingly enough I once took a class taught by Szczepan's sensei where we were doing shiho nage. I was training with a big yudansha and we were resisting eachothers technique by keeping our elbows in and low and sinking our weight down. After about five minutes of getting nowhere, my partner asked the sensei: "What would you do?" His aswer was "Something else".