I've never figured out the numbers, but I know mac/chap-strutted cars are affected more than some other types. Consider that at stock height, your LCAs are level. Now, when you lower the car the geometry at the top of the strut doesn't really change appreciably (angle is computed as perpendicular to the strut axis), while the LCAs are now at a slight angle.
Consider that for a 1" drop in CG, the LCA adopts about a 1/12 slope (which I can't remember how to convert...) Anyway, you can see that the drop in roll center will be considerably greater than 1".
Puhn's book has all the formulas, but I haven't tried actually measuring my car.
