Why not round off the end of the brace and simply drill a hole and use glue and a #10 screw to attach your brace to the side, then plug it with a piece of dowel, cut flush and finish? This should hold your flak vest, LBE, gas mask and helmet with no problem. If you really want to recess the brace progressively deeper then you will need to chisel it out by hand.
Fly ARMY!
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Mike |