Im confused? You saw "yes" that the coupe seat fits a 4 door but then you say a "coupe fits a coupe and a sedan fits sedan". I assume you were talking about the Si part of it. My question was poorly worded. I have a 2008 Si sedan and the back seat isnt great. I found a Si coupe with a good back seat and want to know if the size is the same and it would fit in the sedan?