I am in the middle of building a set of caster/camber plates. I intend to cut the strut opening bigger to install these. I can make then adjustable for caster or camber, but not both.
If I follow your suggestion then I set them up for camber. I have camber adjustment bolts at the knucle/strut mount which I should set for positive camber for tire to strut/spring clearence and then get the required neg. camber at the upper strut mount camber plate. Makes sense.

So my question now is: Then how do you adjust caster?