Been lurking for awhile and this is my first post. Heres my situation. I have an Englander NC30 and i need to install a liner 15ft down a 7in ID clay tile. I know that a 6in liner even un insulated will be tight but that is what my stove is calling for. I intend to insulate the best i can with a pour down. My question is whether or not going with a 5.5 square flex liner will be ok. My thoughts are the square shape will give me close to equal volume and actually give me more area to fill with a pour down. Im hoping to get as close to 0 clearance code as i can. Im trying to be as safe as i can while still performing a quality DIY install. Thanks