I just went through this with my Landy rockers hitting the stock valve covers. I dimpled the valve covers where they were hitting. With the wrinkle paint, you can't even tell. That helped, but there was still a place or two that just touched.

I used the Fel Pro Performance gaskets, which are 2 rubber/cork gaskets laminated to a wire mesh. They are really thick.

Then I put a washer under the spark plugs to space the tubes up. No more rocker to valve cover contact and no other problems. Probably not a perfect fix, but it seems to work.

And I would like to try the silicone gaskets mentioned above. The rubber/cork seal good, but need several re-torques.