Camber plates is FRS thinking, those numbers you want is more FRS thinking. Remember that scene from Matrix where he says "NEAL, FREE YOUR MIND!"
The Miata is not an FRS, you need to free your mind of FRS thinking or you will get the setup for Miata all wrong...no front strut suspension here so none of that FRS setup or thinking is relevant here.
Miata has far superior proper front double A arms with massive range of adjustment once the car is lowered. Nobody uses camber plates on the Miata because they are not needed, easily over 3 negative camber with moderate lowering and ultimate amount depends on how low you go. Your perceived need for 3.5 negative camber ignores the fact that camber curve is MUCH more aggressive on this car front and rear so you don't want or need FRS strut front suspension numbers anyway, again, got to free yourself of FRS thinking or you will be going the wrong way on setup. I can run any camber I want on my race Miatas and I don't run that much, don't need that much, tire temp probes tell me that we would not want that much. Look around, spend time in autocross section of miata.net, and you will see nobody using or talking about camber plates on Miata.
I am not a fan of Carbotech. We did carry them, we discontinued them. Far too sensitive to break-in, lots of other choices that don't fail when you don't follow break in procedure to the letter.