Drilled light baseplate and located to flange with cleco. Drilled inbound side and hot glued on a nylon tap washer, with the post located in a hole in the inbound wall. Juggled the light until I was happy with the position, and hot glued a block of 1" H45 to form the bracket.
Pulled it out and shaped the H45 until the shape pleased me, applied a flox fillet to the base and around the tap washer, then 4 x BID between the base and the H45, 3 x BID over the tap washer.