Back in post #18 I attached a dorky little side-view diagram of the effect of tilts on the plane of focus. It's attached again here, click to enlarge:
When you adjust tilts, whether you use axis, base, or asymmetric tilts, you're adjusting the position of the heavy black line that shows the plane of exact focus. Asymmetric tilts are just one way of doing that, whose intent is to cut down on iterations between focus and tilt adjustments.
Once you have that plane, because real scenes have some depth, you need to stop down the lens to extend the forward-back extend of the gray band, which shows the depth of field. When you have used tilts, the gray band is also tilted.
One way of determining the depth of field you need is: after you have the tilts set, adjust the focus as far back as needed, as far forward as needed, measuring the difference between these positions. The distance between these positions can be converted into the f-stop you need to stop down to. This is what the Sinar DOF calculator knob does. You can do this without a Sinar, if you measure and then calculate the necessary DOF, or use the Rodenstock DOF calculator wheel that Bob mentioned.
I'm not saying anything different than what Doremus and others have said, just suggesting that it will be helpful if you look at the diagram.
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