We've decided to replace our Englander with a PE Alderlea, and all clearances and connections should be OK except for the OAK. The Englander takes a 3", the PE takes a 4". Our OAK is a 4" for about 20', and then downsizes to a 3" through the floor, the wall, and into the stove - about 10'. How much of a problem will we have using a 3" pipe for 10' of the run and then upsizing to a 4" connection to the stove? Replumbing for a 4" through joists, walls, and doors is not in the works!