well, against most all recommendations, I had a valve cover off, one that is always seeping oil towards the back
on the passenger side. Not having new gaskets, I blotted dry the existing gasket that was tacked to the valve cover
from initial installation a few years ago. I then took some black form-a-gasket, and spread on a thin layer with my finger, on the formally oil
soaked cork gasket. I then installed the valve cover, made it finger tight, let it sit for about 4 hours, then tightened it down, as normal.
For the first time in 10 years, I'm getting no oil seepage in that area. I'm sure my leakage has been due to the after market valve covers
not being perfectly flat.
So, one point for putting form-a-gasket on top of the cork gasket, and having no leaks.