I am Joseph Shropshire.  My sons (William 15 and Lucas 13)and I worked with Fusion 360 to come up with 2 designs.  The first is meant to span your 2 1"x2" boards to react the moment cased by the cantalever that is the spool holder.  The second is a simple clip on design that is meant to attach to the 1"x2" furthest from the wall.  We believe that this will have to be a Nylon to have the appropriate durability and stiffness to clip on and to hold the weight.