OK, haven't any of you guys ever seen an old VW Dune Buggy from the 60's and 70's that always had deep Dish, or reversed wheels on the back. Don't you remember how much negative camber they had? Especially when ever they were launching. It's the same principle on any car that has an IRS.
Adding a spacer to kick the wheel out 2", is essentially no different than installing a reversed rim. Either way, the tire is going to be further away from the point where the axle pivots at the outer CV joint.
In essence, it's like your installing a longer axle shaft, that is going to put more leverage on the springs, and create more negative camber. At least that's the way I see it.
But maybe the rear camber arms will prevent it from happening, I don't know.