Ed, on the Somethin'Extra/Great Planes .40 single float combination, the protrusion of the float was dictated by the shape of the pieces. with the step located 1/2 inch aft of the spar (CG), the nose of the float ended up 4 inches in front of the prop disc. Another aspect of the single float rigging was to shorten up the float struts so that the 11 inch prop cleared the top of the float by only an inch. I reasoned that lowering the thrust line would minimize the pitch down moment on throttle application. Splash rails on both fwd chines have made spray through the prop not much of a problem. In rough water with higher swells, the two float rig with the floats 2 inches below the prop disc did work a bit better. The single float setup works very well on calm to 3 or 4 inch wave water.

I had thought some about a retractable float machine also, and have some concern over extra weight and CG shift during retraction. Will be real interested to hear how your experiment works out.

Paul