Another reason the MP cast covers can be difficult to seal with thinner, less compliant gaskets is there are irregularities cast into the sealing surface area.

Even if the covers aren't warped, the gasket surface isn't "flat"(smooth).

Brad, if you have a sharpie/marker, you could color up the upper v/c rail on the head, lay the gasket on it, and scribe a line of where the inner edge of the gasket sits.
After pulling the gasket off, you'd be able to see how much overlap there is.