Engine build on the brain

The problem I see is that with a solid lifter cam, we have to guess at the true zero lash point.
the general idea used to be, to add one cam size to the one you got, and work the calculator as if it was a FTH.
Or if you don't already have a cam, then work out ,on the calculator, what you want; then order the next bigger cam.
But with modern tight lash cams, this does not guarantee success.