I think I might just answer my own question as I have just watched the Tushie rigging DVD and this might help anyone else with the same question. Negative outhaul or not enough outhaul can feel uncontrollable and bad to handle. Unless you are going for the world speed record and have alot of downhaul and really over powered this gives you massive off-the-wind speed. The down side makes it harder to get back up wind. As decrepit has said, on the DVD, it said this only works with cam sails. I'm sure if you delibrately rig these sails way outside the recommended settings they are still usable. If the sail is resting on the boom, as you sheet in the power goes onto your backhand causing the rig to drive the board sideways and you won't go upwind. The DVD describes this little outhaul rigging like hanging onto an umbrella in a gail. It puts you in conflict with the rig and you take on a wide arm, squatting stance. I'm stoked this DVD has answered my question and I highly recommend watching it as it has much more on rigging Tushies.