A little bearing grease will hold it in real nice.
I have been told by several people to keep the gasket sealer away from my head.
I pinched the o-ring gasket once during installation, just used a little red rtv, has worked good for all last season. I intended to just get a new o-ring, but since it has held up, it is permanant until the next tear-down.
Anyone know exactly why rtv is a bad choice for sealing up a cool head?