So maybe there is an obvious answer I'm not seeing but if there is such a range of speed between the water rudder and main rudder both being ineffective and having no directional control, but one of your problems being that the ski's if not extended exactly the same amount causes a turn, then why not allow the ski's to be controlled independently mixed to the rudder so that they can give some directional stability? I understand that they need to extend fully to reach the angle of attack needed but while doing that why couldn't they be allowed to move to turn the model and avoid situations like heading towards the reeds?