We want to install a wood burning insert in our small ground-floor fireplace. It's been blocked off for years, but we think it previously had a propane heater. The opening is 24" wide, 16" deep, and 27.5" high. We want an insert that projects into the room. All that I've found that will fit are Buck model 21 and Lopi Answer inserts. How do these stoves compare? If the existing masonry chimney is a straight run except for the connection end, would a solid stainless liner be preferable to flexible?