I would approach this a little cautiously as to how much shim. When I tried to fix my caster problem, IIRC, I tried something like handy 1/8" washers, with a slot cut in them so they could be dropped over the bolt. It was way too much - the steering was terrible, light, and zero self centering which meant you had to wind the wheel back to centre after every turn. Just doing the inner mount wont have as much of an effect, but be prepared for multiple tries. Suggest you get a real measurement of your camber before, with the car level, and all heights set up as per the manual. I found the subtle curve of the front guards always make the fronts look like they have negative camber. The book says 0 +/- 1degree. Some cars are sensitive to camber in small amounts - MX5s are much better in corners with -1.5d, rising to -2d for track work. Std is -1.0d IIRC.