Offenhauser Triple Carb Setup
 

I purchased the Offenhauser 5205 Triple Carb Manifold from summitracing.com. My problem is that the curvature of the manifold does not fit the curvature of the Offenhauser. The intake manifold is more flat then rounded and is more then the O-ring in the Offenhauser can compensate for. Is there a solution to this problem, is a heavier O-ring available to use?