Compression...

I would expect that stackable gaskets are designed with that possibility. MLS (Multi Layer Steel) gasket designs are not stacked. They are fastened together when the right thickness has been reached. You cant put two on top of one another and expect them to seal. They wont. I have heard of some guys experimenting, but that's short term. If you're building an engine, you design it and build it right. Stacking gaskets is the equivolent of tying a car door shut with mechanic's wire and calling it a permanent repair. Sure, it will work..but for how long, and under what circumstances.

69- I've seen thier quality in terms of parts and labor first hand. They are simply not worth what they charge.