To INCREASE compression ratio, you need to LOWER the head, not RAISE it. Decking is when you mill the heads slightly to INCREASE the compression ratio. Unfortunately, that can cause a whole lot of other issues that will need to be tended to such as increased engine knock (detonation).
Doubling up on the head gaskets is an old trick to LOWER the compression ratio so the engine is more compliant for the installation of a turbo or super charger.