needa glue or epoxy recomendation...?

i just put up a wood mantle on a brick fireplace( rest on two brick arms, then . i used two tapcon screws angled into the top into the brick face, so i should be fine, but i was hoping to add more security to it and therefore orignnaly thought of using L bracket behind the mantel that i would attach to the brock and backside of the wood mantle, but i cant as its too close to the wall and therefore cant get a screw or screw drill back there, so i though of using some kind of bonding agent (epoxy, glue. etc...) to give it exra support. the Lin a prfect world i would find soemething that woudl have a super high stregeth test.