I am restocking my Citori with a Wening American Trap Stock. My question is regarding the different shapes of recoil pads. Pachmayr Trap models have a concave face, their skeet models are flat, Gooey pads are convex and Kick-Ezz has several shapes, flat, modified trap & rocker shape are a few. When anyone replaces a recoil pad, what determines which shape to use? Past experience, trail & error or what? Thanks for any input. Ed Fish Racine WI.