Interesting thought. I would first be concerned about flutter of the foil if it kicks up while the boat is moving at any decent speed...that is, unless you built in some imbalance stability into the foil - but that would result in undesirable drag during normal attitude. I know first hand that control surface flutter can be violent and result in the death of a model airplane!

The geometry between the pivots and the line seems to be a bit off - but that might actually take care of the potential for flutter if it can be arranged put the foil at a slight bit of a "down plane" attitude when it is released.