Does anyone know if both center holes on a duravent wall thimble are supposed to be the exact same size? When I installed my wall thimble then ran my pipe through the wall, the pipe fit snuggly in the center hole of the inside thimble piece. However, there is considerable play around the pipe where it goes through the outside piece. I would think this should be the same. I am starting to think that maybe I received a 3" and a 4" together. Or am I missing something that I should have done with the outside piece?