After installing my new Jotul F 600 wood stove on my fireplace hearth extension I've been monitoring the temperature on the underside of the mantle. The clearance called for is 26" for an 11" mantle and my stove top is only 22" below my 10" mantle. When I shot it with my IR thermometer I was getting a reading around 170 F with a 400 F burn going in the stove. I could put my hand on the mantle for more than three seconds without discomfort, but I didn't have peace of mind, so I decided to install a heat shield under the mantle. I had some left over sheet metal from making my stop off plate for the fireplace, so I cut a piece 48" x 9 7/8" for the shield. I attached it with some short drywall screws and used 3/8" thick slices of bamboo for the ten spacers. It is not very noticeable when viewed from the front. I know a one inch air space is normally called for when installing heat shields, but since this application was so marginal I decided to keep it closer to the mantle for aesthetic reasons.