I RTV a cork gasket to the valve cover and then only lightly snug it make it flat... once it's dry I give it one last little snug and then fire it up n drive it.
I do similar. I don't use RTV, but I do make sure the valve cover rail is FLAT and then apply some 3M yellow weatherstrip and stick the valve cover on and let it set up. Works every time. Your way sounds good too.
