Used OE and Vesrah composite head gaskets usually mic out around .043." .An Athena gasket won't compress anywhere close to .017", and no matter how you look at it you'll wind up raising the deck more than .010" with one of those. Bottom line: Athena uses 1.5 mm. (.060") material because it's off-the-rack stuff and they can avoid the expense of nonstandard stock. 5twins, the rest of the gaskets in the Vesrah set will be made to OE Yamaha spec as well--thicker and tougher than that slick green stuff you get from Athena. I suspect that Vesrah may have been the OE manufacturer.