I have wondered about these spacers too. It seems that using these (Or something slightly thinner) along with Moog K-7103 offset UCA bushings would allow you to have some acceptable amount of negative camber and a bunch more caster. Since the alignment cams allow such a little range of adjustment, little tricks like these can help fine tune the settings while allowing the car to maintain OEM durability of stock based parts.
Being cheap always helps as well.