In reply to Alex Newton:
Adding a backboard adds strength to the mounting, but the other reason you might want one is to stop your fingers going over the edge of the board when using the slopers, as that would make them a lot easier to hang.
Would you be drilling it directly into a wall above a door or other opening? If not then your legs will be against the wall so you won't be able to hang in properly. A better idea would be to construct a frame that sticks out from the wall with a backboard to attach the beastmaker to. Look at the beastmaker mounting guide.