A mantel should stick out at least 6 inches (15.24cm) from the wall. It's the perfect depth that allows you to have a mantle effectively deflect heat without compromising aesthetics. You can extend it to have more depth for your decorative pieces, but we don't recommend having it less than 6 inches (15.24cm).
How do you pull down a mantel mount?
https://www.youtube.com/watch?v=0_PKegSmGVI
Is mantle mount worth it?
While this mount is expensive, it is definitely worth the money. I imagine it would be even nicer if I were using it for the intended above-mantle purpose, but just keep in mind the difficulties of following in my footsteps if you choose to buy it for that purpose.