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Phil M. This model of the FoilMount is for boards with a "ridge" down the board in the mounting location. The bottom mounting area still needs to be fairly flat and you can get away with small amount of concave but still shoot for a fairly flat area. The ridge mount has a cut down the length that allows it to bend side to side...each side is till flat which is why it is perfect for the bottom "ridge" application. Works great!! Real is the best!