I was noticing in the plans that the seat base and seat back are at 45 degrees to each other. At first glance, it seems like the rider would have a tendency to slide forward on the seat base, but the whole main tube is slightly higher in the front - I can't tell how much from the plans, but does this give you some help with staying in place? Does anyone know what the main frame tube angle is compared to the horizon (zero degrees horizontal reference?