I picked up a second hand Quadrafire Castille and I would like to set it up temporarily in a spare room but it was set up with a vertical chimney and I would need to direct vent it straight out the back. I know it is not the best way of venting but it is quick and easy for this temporary location until we refinish our house. I believe the installers used silicone to hold this part on. How hard can I pull on this part to get it off?