I haven't read this whole thread, but it is founded on an error. Multiplying length and girth (the OP says "thickness," but the figures that he gives as examples show that he is talking about girth, i.e., the distance around, not the distance across the shaft) will yield a figure proportionate to surface area, not to volume, and therefore not proportionate to mass. You would have to multiply length by the square of girth to get a figure proportionate to the mass of the penis.