No shims under blocks is equivalent to 3A on standard blocks. I personally wouldn't run them any higher than that on med grip asphalt.
So far the kit seems to be a massive upgrade in the traction department. The extra rear flex gives alot more rear traction than the standard kit which means the car can be pushed alot harder with confidence. The flex is very balanced left to right which makes the car more predictable and the narrow chassis means less scraping on sweepers.
The other big improvement is the ease of adjust-ability with the split and solid blocks. No more moving hinge pin blocks or binding arms etc. A refreshing change from the standard setup.
Hope that helps!