Any consideration given to using 316 SS Rigid smooth liner? They come in sections and they are a heavier guage SS as well.
Flex liner is difficult to clean corrosive fly ash and /or creosote from the spiral corrugations, which shortens the life of liner greatly.
Corroded liners can eventually crumble, if not detected early, and collapse inward and downward and possibly block much of the flue gases from exiting the appliance and there by backing up those deadly gases into the living space.
Wood's creosote is alot less corrosive than coal's fly ash...don't let the track-record of succesfull wood burners w/ flex liners fool you.