Then test in a simpler way.However, I'm a fan of simplicity.
I'm not trying to have "the last word," nor am I trying to antagonize you. Quite the opposite - you brought a legitimate and interesting question regarding DOF to the cafe in a very well-articulated way, and I want you to learn the answer to it. Many have offered constructive advice. You have nothing to lose and everything to gain by following a little more of it.I feel like I've been extremely thorough with my testing.
Best of luck - either in learning the answer, or being content in not doing so.