There really isn't a need to stack gaskets - you're less likely to have a leak if you use only one, and put Curil T on them (or similar product).
I've even seen some builders recommend Curil K2 on the shim on the side mating to the cylinder, then the Curil T on the side to the case!
Places like Flatout Gaskets
http://www.flatoutgroup.com can make shims in whatever thickness is needed in basically no time flat - they make all the ones I supply to my customers, out of copper, stainless, or carbon steel depending on the customer's application.