Hello all,
I have had an SAH aluminium rocker cover on car for many years and use the standard cork rocker cover gasket. None of the proprietary gasket sealers are very effective from a practical point of view (all will seal fine). But if, as I said earlier, you use contact adhesive to securely fix the gasket to the cover, it is easy to fit and I re-use the same gasket several times. It takes a little time to do but saves time in the long run and it doesn't leak.
Alec