Don't worry too much about cutting the gasket. Beez and Cactus Dave are both right. In the, uh, old days we used to make all of our gaskets from blank material. (Remove the studs and stick the oiled surface on the gasket material to mark it.) We did not use sealers. We just put them on dry. We would purchase different thickness material to get different deck height. Sometimes the sealers will make the gasket "walk". Not always, but I found that out the hard way once before a race....