Ed, you might try emailing or calling Wray Schelin (Sha-Leen) at Pro Shapers for his advice on how to shape that.
He's about the best there is and runs regular classes on metal shaping.
My guess is he'll tell you to segment the buck more with narrower strips slightly apart to get the curves and flow you need, but whado I know..... Tell him what you have for tools available and see what he comes up with.
Tell him that Gordon from the Porsche 356 club sent you - He should remember.