I believe that the bolts have a shoulder on them so the will only go so far into the head, which limits how much crush you can put on the gasket. So just snug them up and give them a hair more so they don't come loose. I could be wrong though. Oh a good idea also is to take something like carb cleaner and clean the surface of the head where the seal sits, getting all the oil off will help the gasket seal better. Also it isn't a bad idea to change the oil when you are done, before you start it up. Just incase some dirt fell in or something.
