ok, i have a us stove company 1100. WAS going to go single wall inside with a heat shield but decided to go double wall dvl instead. maybe i'm missing it somewhere but do i HAVE to have a flue damper? my local dealer sold me a stove adapter, telescoping vertical rise, 90 degree and 24 inch horizontal run. no flue damper. he doesn't sell us stoves but said that newer stoves don't need a damper. true? thanks.