I think Paul MacCready really solved a different problem. Earlier man powered aircraft (SUMPAC, Toucan, Puffin etc.) had been based on glider (sailplane) technology that emphasised the highest possible lift/drag ratio achieved by large span high aspect ratio wings and careful control of the aerofoil shape. The span and aspect ratio make the aircraft complex and comparatively heavy. MacCready realised that if the aircraft was made much simpler and lighter it could fly at a lower speed and although the L/D ratio was poorer (all those bracing wires!) the drag would be lower (V2) and the power required (V3) much lower, within human range. The quick to fail, quick to rebuild was a consequence of this simplicity.

Incidentally the photo showing the "speed ring" is nothing of the sort. Speed to fly rings are about 80mm in diameter to fit on an instrument face.