I'm trying to vent an older Schrader stove and the starter collar is an odd size, I measured 7 5/8". The 8" stove pipe is not a good fit and crimpiing it doesn't help either. I replaced all of the original single wall pipe that the customer had put in originally (he had a chimney fire) and used double wall DuraVent 8" going from the top of the stove to the ceiling support box. The rest of the way up I used 2100 degree pipe. I tried an adapter that DuraVent makes a double wall that's 7 1/2" (inside at bottom) X 9" (outside at top) but still I'm still having the same issue.The height of the venting is more than the mininum height and runs all the way above the peak of the roof, but we're getting a down draft (only when raining) and theres a leak at the starter collar. Does anyone manufacture pipe for this stove anymore? I think the best option is to replace it (the stove)due to the lack of efficency, but the customer wants to keep it. Any help would be appreciated.