This is not an entirely new topic, but has been dormant since 2002.
It was suggested to the previous enquirer that he cotact Tony Paulin of FE-Pipe. I wonder if anything came of that?
The problem is that the Caesar II flange leakage calc accepts all inputs for checking a ring-type joint, but it seems that the effective gasket modulus is un-determinable.
Has anyone else worked through this problem since?
Perhaps I should try and take it up with Tony Paulin, if he is still contactable.

Tony Paulin can be reached at Paulin Research Group, tony@paulin.com.