Gasket Stuff
Chris is right, by doubling up either gasket the compression will descrease slightly because you are effectively making the cylinder taller in each case. I run base gaskets from a friend that builds micro-sprints which are about half the stock ones. This is easy because they all run CR250's or a few run YZ250's and I have a CR.
One cheat you can do is to take a little off the top of the cylinder and run multiple base gaskets or a sleeve to make the exhaust port higher. This will allow your bike to rev higher. But I think that if you are going through this work, you might as well just get the top end ported properly.
Stan