Aah congratulations. It's a classic. WHile its tempting to mount the rear strap off center to ba able to crank the board more with the back foot, I would say the board works much better with the single rear strap mounted in the center. There are two reasons. 1. Using the rig and front foot to initiate the turn instead of the back foot will let you surf the board much better. SO bend you knees, "crouch" a little and let the rail do the worj and even this super wide board will turn very well. 2. When you get to the top and want to top turn, you will have very little power if you have your back foot over the centerline of the board. You feel much more balanced when hitting some white water and also be able to turn in "clean" water much better off the top with a center mounted rear strap.
Good luck and tell us how it orks out.