A little bit of advice from the resident chiropractor...based on back position you would do a lot better if you could move your feet under you (floorboards or mid mount pegs), have a back rest and of course more cushion on the seat. You want to take the pressure off your tailbone and keep your low back with a normal forward curve-not slouched. There are lots of exercises you can do to help too. Ab crunches and hip tilts for starters. As everybody else just said who has been riding a lot longer than me...but I do know backs
