Can I run 6" flexible liner through my 8" double walled insullated pipe? I bumped into the pipe the other day and I wasn't happy in the way it was put together....it was pipe that had been removed and reinstalled and I think some of the grooves the pipe locks together in got bent and didn't fit back together the way they properly should. I would like to stiffen up this pipe and then run a 6" flexible liner down the inside ... is this proper and safe? What are your thoughts on this strategy?