Didn't mean to sound like I was blaming you, rather just trying to troubleshoot it. Was in a similar position myself with my previous Century insert -- also too small for the house and trying to coax more heat out of it. For awhile tried putting an old water heater fiberglass blanket around the back and top of it to get more heat into the room from the front. Fortunately the stove was just too small and was probably impossible to over fire with what I was loading it, so never had that problem and didn't keep the blanket on there very long. But while I had it on it did increase stove temps about 75-100 degrees though that was only to as high as about 650. Eventually found that removing the surround worked better in getting more heat out of it. Hopefully, you'll get some more definitive answers when the sweep comes. If it were me, I think I would be putting in a warranty claim on the liner though since you do seem pretty confident there was no chimney fire. And you also might be thinking about an insurance claim, if you haven't already.