I've got the 31.5 Airborn for the crappy on-shore beach break windy conditions I often surf in. In small waves even at my weight of 68kg 150lbs it is heaps of fun. Also have a 7'7 x 27 for cleaner days.
Think the Airborn needs a slightly different way of thinking, its not just about going as narrow as possible, the shorter length and greater width combined with fine rails gives it a super curved outline that turns fast and effortlessly.
Have a look at the videos of Colas surfing on a short wide Gong Sup, gives you a really good idea of the way these boards can perform.
www.seabreeze.com.au/forums/Stand-Up-Paddle/SUP/Some-fun-waves-in-Hossegor/To get a similar 'feel' to the 9' x 28.5 custom you currently have the 8 x 28 Pro would be my pick as well. Awesome board, almost as good as the 7'7