Air Gap Machining

Ok, here goes. Trying to put the Air Gap intake on my magnum small block
408 build. Intake has huge gaps and slides side to side with all gaskets in place. Called Dave at hughes engines he said to remove the china wall gaskets and use silicone there. Then he had me measure the gap between the gasket surfaces (between intake and head) .003" at the top and .007 at the bottom. Dave says to have .016 shaved off of the top down to .000" at the bottom. This is to allow a wider gap at the top so when it is torqued down it will lay flat. My question is... is this really necessary or do you guys just simply bolt them on?