That's a quite common place for them to leak.
Don't use RTV on the gasket sealing surface, there is no need.
If put on correctly, it won't leak.

When you put the gasket in the valve cover, put just a tiny
drop of RTV in the gasket grove every 4 inches around the cover to help keep the gasket in the cover.
Turn the cover upside down on a piece of cardboard and put
a weight on it (something like a car battery) and let
it sit for 30 minutes or so.

Just before you put the valve cover back on, put a thin
layer of RTV over the seams of the half moon cam plug
at the back of the head. Also put a tiny dab in the
corners of the front most cam tower (the one the seal goes in).
Then, put the valve cover on and tighten the to spec,
starting with the center and working to the outter two.
Don't torque them down to 7lbs right off the bat.
Start at 3 or 4 and bring them down slowly.