Rocker cover has step-screws as shown by a nice picture by our Forum member
DesiBike on his bike when he replaced the gasket
(below). These screws have only limited travel - only up to the height of threads on the screw. Once tightened to that distance, the screws cannot be tightened further and the gasket is not compressed any further. The only solution is to replace the gasket.
May be the screws are slightly loose, but I doubt that that is the real reason for the slight oil leak that you see.
As pointed out be Portisheadric, some oil may be going past the O-rings seals on the screw heads. Worth looking into them as well.
I think there are quite a few bikes with that type of oil leak. My G5 also has a little oily stuff coming out from time to time. Sometimes I clean it but for the most part I ignore it. This reminds me why it is REally a Royal Oil-Field - it is still a 1950's bike !
PS - Arizoni you just beat me to it, we were both typing the same thing at the same time
!