We've found the insert that both the wife likes to look at and I'm comfortable will do what I want it to do. We've settled on the Jotul 550 even though it's more than I wanted to spend. Our existing fireplace dimensions look to all be perfect for this insert but the one question asking for a minimum 51" from floor to mantel height. We only have 45" but we really don't have a true mantel. We have basically a 3/4" painted board that covers the sides and top of the brick that creates a 3" shelf above the fireplace. We don't have a true mantel that extends out inches over the fireplace front. Does this matter?