Just my personal impression, the copper must be indestructible compared to any fabric, after annealing and correct tightening sequence it forms itself perfectly to the surfaces down to smallest scratches, will withstand any pressure, just needs one re-tightening after some hundreds miles, then forget all about it. On the other hand, if anybody came up with some modern material that had proved itself in practice, I'd be glad to try it.
Trying a gasket-less solution, if the surfaces were skimmed - perfectly +++++ -, but would there be any real gain compared to a well fitted gasket ? (one thing, should be next to impossible to bend the cylinder head when tightening the bolts).
