Strong I Right Ace Rt. 515 HB Flat vs. cover 3 takes advantage of stretching the defense horizontally.  The flat routes by the Tight End and Back takes the flat players wide leaving the curls wide open.  Vs. m/m coverage the curl routes can be ran deeper.  This puts pressure on the defensive back to protect himself vs. the deep ball.  Then the receiver can snap it off at 18-20 yards and work his way back to the QB for a relatively easy completion.