One way to get the stove pipe from where I want to put a stove and to the port in the chimney is to run between the water heater and the furnace return duct. I don't think this is OK. So my question is - if I use double wall it should be cool enough to run that route - but now I am unsure if it would be ok to have a foot coming out of stove, a 45, 2-3 more feet, and another 45 into the chimney. Too long to maintain a draft? Too long to start a draft? Won't even fire?