Osburn 2400 insert - cleareance to combustible mantle shelf problem

All,
I need your help. I really like the Osburn 2400, but the specs call for at least 25 1/2" clearance to combustable mantle shelf. My mantel would sit 20" above stove. The mantel is wood and is anchored pretty good into my brick fireplace. Wife does not want to see it raised. The Osburn 2000 insert comes with a a mantel shield option which reduces that number and would work for me, but the 2400 does not. I don't know what to do. I want the bigger insert. I'm also still considering the Lopi Freedom bay and have a rep to come show me the BUCK 91 insert on Friday. But, this issue with the mantel is driving me mad

not the best pictures but I will take one when I get home from work. The distance between the hearth and the bottom of the mantel is 43"

I found a mantel shield online "homesaver" however, it is only 10" deep. My mantel is 11" deep. I can't find any others online. Apparently Osburn says that you can use the 2000 mantel shield on the 2400, but it's $100. I may just have to take the hit.