Ram Air Cleaner Base

I'm running a Mercury Cougar hood scoop on my 73 Swinger and I'm looking to seal the air cleaner base to the hood to make it functional.

I'm using a 11" K&N X-Stream element and lid. I'm batting around the idea of using a non-stick 12" cake pan to make a new air cleaner base. My question for those who know more than me about Ram Air, will the 1" difference between the "cake pan" air cleaner base and the filter be enough to allow sufficient air (cfm) at full throttle? I'm wondering if I would be better off with a 14" cake pan.

A cake pan, ram air and a Dodge Dart...I know...there's a joke in there somewhere. :D