I pretty much ripped out my liner, and found the flex pipe at the end is all oval flex, it wasn't round that they ovalized at all. I put a 2x4 into the ovalized flex and spun it around. That removed a bit of the ovalization. I then put a 2x6 into it, and spun it around. That makes it pretty close to being round. See any problems structurally with doing that? Pricing stainless flex pipe, it would be around $300 for me to replace the small portion of flex at the end. I'd like to use what I have. Also, found out I don't have to cut the damper. The opening of the damper is the same as the opening of the masonry above. So, think bending ovalized flex pipe to be round structurally weakens the flex?