Once I scraped all the caulking and sh#t out of my way, I set the lamp mount plate in place then scribed lines either side to mark the position of my wood hardwood blocks either side. I had some 3/4" American cherry kicking around that fit the bill. Blocks were about 7 - 7 1/2" tall by 1 1/4" wide. I chose 3/4" material for good screw purchase. Used 5-min epoxy and spring clamps to hold them in place. Boom done.