That is what I was considering doing, using the rubber seals and adding some sealant to the top and bottom. I think the reason we had no problem getting the rubber ones to seal with the tin gasket is that the composite ones are a lot thicker, moving the manifold up higher and off of the rubber ones a little. I also put a dab of rtv in the 4 corners of the rubber ones as that is what they usually tell you in the gasket instructions.

Don