How does the rail become afixed to the bar top? I’m assuming it need to get glued down so you don’t have to plug holes on top? The instruction manual makes no mention of this.
You typically glue the arm rail down, then drill pilot holes from below and use the shortest screw possible (1.25″ usually works well). Use clamps to hold the rail down until the glue dries. The pilot hole keeps your expensive arm rail from splitting.