Engine Replacing the gasket on a gt40 head need some advice

Over the years I've tried several different way to seal lower intakes. These are the instructions from felpro for a 1250 3s gasket set. Usually, I use just right stuff at the front and rear valley seals. The instructions show how to see how large the gap is between the upper and the block. I've seen some engines sit down almost on the rails and others that have had up to 1/4 gap. I've even seen a couple where the angle of the intake didn't match the angle of the block.

This is the one area where you could fail any way you do it. This time around I used the cork gaskets that came with my gasket set. I trimmed them to fit the valley and then stuck them down ( they come with adhesive on one side ). After that I put a 1/4 bead of right stuff in the corners and I put a small 1/16th bead of right stuff on top of the cork gasket.

I've tried soaking the cork gaskets and using shellac....held for about a month ( the cork has changed now so that isn't done anymore ). Tried just right stuff. Lasted usually a few months to a year. The blue rubber has never worked for me on the valley. They always find a way to leak no matter what I do. The trick to all silicone is that it has to be thick. It has to be able to resist the pressure from the engine pushing on it.