Typical camber gains on McPherson setup?

I know this is hard to answer exactly, but how about some general range sort of answers?

Here's the question: I know McPherson is not the best setup for camber gains in bump, and double A-arm gains camber in the amount of about 1/2 of the body roll (for a miata at least). Meaning for 2° of body roll the wheel to chassis camber will go more negative by 1°. This produced a static camber goal of -1°, with roll stiffness of 2°/g. (got this info from GRM)

Beyond this, I am looking for an educated guess of the camber gain on a McPherson setup, in particular on mazda3.

anyone?

mcphersons have none whatsoever. You have to have more than one flex point to create camber difference at different strokes. There is only one joint on most mcphersons setups, so there can be no change.

I know this is hard to answer exactly, but how about some general range sort of answers?

anyone?
Easy to answer.
A MacPherson strut has in fact a negative camber gain in roll.
A SLA suspension can have as much camber gain as you want in roll. But it depends where the suspension pivot points are located. Usually you want to consider other interrelated aspects like-- Scrub, roll center height, etc. before you get frisky with trying to keep the tire vertical in roll.

Easy to answer.
A MacPherson strut has in fact a negative camber gain in roll.
I think this will probably depend on the car in question, but if the lower control arm is perpendicular to the strut tower mount when the car is at rest, whether the arm rotates down or up, it would ever-so-slightly pull the lower portion towards the car, that would be positive camber.

even if its not perpendicular, it would only go negative in one direction, and for a very small portion of the total throw.

It would be very slight though. Nothing compared to a more traditional twin arm setup, as you say, depending on pivot locations.