I'm working with a 4-stroke so I've replaced all but two clutch cover screws, and the four screws that bolt the engine to the plate with allen bolts from home depot. Then I locktited the ayche ee double hockey sticks out of them. I would recommend anyone with anything but allen bolts on their engines to do this. It will allow for tighter fastening and less odds of stripping.
Locktite. Learn it, Love it, Live it.