I bought an old house that used to have a wood heater and need to know if the cover on the square ceiling support box is designed to be removed. It has one screw in the front that I removed, and I can't get it to come down. I wanted to put an 8x6 reducer pipe in and use an old wood heater while we are remodeling but no one seems to know anything about how to remove the cover.The pipe on the roof is 8" double wall and 6" single wall on the heater. Is an 8x6 reducer pipe what I will need? Thanks for any help. I asked around at Home Depot and Ace Hardware but no one seems to know anything.