The best place to get this trophy is during the driving section through the woods in Triple 6's chapter. There are a total of 3 cliffs to jump across (the first being in the form of a cut scene). When you reach the third cliff (the one with a play card right on the edge), boost while jumping off (push up on the L3 stick) and the S grade jump and trophy should be yours when you land. If not, reload and try again.