Too many 15" woofers in your HT, Bob? 
The ruler test is excellent for focus accuracy. You concern is the image plane (as projected by the lens) not being precisely parallel to your image sensor (or what used to be called film.) If your lens is bent, then your center focus on the ruler might remain the same, but the left and right sides of the frame would not be consistent with the center image sharpness or even each other. Inexpensive kit lenses won't give you perfectly flat focus; that would come from a high $$$ lens or a macro lens. BUT you shouldn't see real problems with the consumer grade lens on a side-to-side basis. And that is the perceived problem we are trying to solve.
I will be in STL on the 17th. If you are working I can swing by the shop and run some tests for you.
Hey!
Well, to test the parallel plan, just move the camera to either side, try to keep the camera parallel and focus on the number the same way, but for some lens the edge will be a bit soft compare to the center because of the lens.
Luckily I've never have to do this since all my lenses and camera seem to be fine.
Thanks Buddy, that's pretty cool.
But I think the point is going over my head though. I just plain don't get it.
If I set the focus to the mid point, set the zoom to "all in, or all out", then move the tripod to where a set point/distance can be read........I think I'm missing something.
Bob
Pretty much, just move as close as you can till the camera can lock the focus.
Love that first ruler photo with only the 20 in focus! 
Thanks, it was just a test nothing special. But yes, at 70mm wide open at f2.8 this zoom does pretty well with bokeh, got that smooth buttery feel to it.
Take care,
Buddy
