This Spratt wing is basically a wingeron type model like the Ninja sailplane. OK yeah, I know the Spratt came first. But the point is that the Spratt moves the control functions to the wing while still retaining the stabilizing effect of the tail surfaces. That flying boat uses the tail surfaces as the vertical stabilizer and a mix of the surfaces and pendulum effect to provide pitch stability for the fuselage as the wing finds it's own flying angles above on it's pivot.

Dick, I know you don't use moving tail surfaces but the model still requires them. The vertical area stabilizes the whole model in yaw while the horizontal stabilizes the fuselage provided you figured out how to let the wing free pivot on it's own but still mix in some pitch control through the servos. If you just joined the servos directly to the wing then all you have is wingeron control to replace the tail controls. To be a true Spratt as I read it the wing has to be free to find it's own pitch angle based on the power to the aircraft.

In any event the point is that if you removed the vertical tail on your Playboy I don't think you'll find that it flies very well.

PS: I've moved this to Aerodynamics as it has nothing to do with building. But it's an excellent discussion. Keep those cards and letters coming folks!