I'm looking to get a insert for our fireplace. Our firebox is on the smaller side, where the opening width is 37" but tapers down to 19" wide in the back, which really limits our selection. The house was built in 2005, and the chimney/fireplace is on the side of the house. I would assuming typical builder style of the time. What would the limiting factors be with respect to straightening the firebox walls to allow for larger inserts?