Yeah, the shims were both one good. The two different bearings are specified in the Vespa manual, the C3 is a slightly higher clearance than the CN, for some reason it is indicated for the flywheel side. Really the difference between a 6202 and 6202/C3 is not much, the clearance scale runs from C1 to like C5, and a CN is right about 2.5, so not much off a C3. I just used it cause thats what came with the rebuild kit and thats what Vespa calls for.
I rebuild mine the no pounding or hammering way, like you, I guess. Freeze the crank, heat the bearing just a bit on the stove and it just drops onto the crank. Heat the large case half, drop the crank in, heat the small one and put it on, let it cool and put the case bolts back in.