Sorry for getting back so late, I was on vacation. I use the Richie S58W tactician surface mount. I mounted a 6" x 6" board to the center of the hatch cover to elevate the compass. A spacer under the board edges keeps it flush with the curved hatch cover. The board has two screws protruding from it. The compass drops onto the screws and a slight twist lock it in place. A ring gasket supplied with the compass and positioned between the compass and the board keeps tension on the compass. Hope this helps. Don