I'm considering a Osburn 2200 or 2400 insert. I like the look of the 2200 with the bay window but haven't been able to get a good picture of the 2400. The 2200 is only $50 more but the 2400 is a bigger insert. Does anyone know the benefit of one over the other? Does the 2400 require an 8" flue? Thanks for your help.