Wow, thanks for finding that article and sharing it.
So I guess the bottom line is that if you increase the radius of your penis, greater pressures are required to produce and maintain a rigid erection, as predicted by Laplace. All the participants in that study had markedly reduced elastic fibers in their tunica albuginea, which implicates loss of elasticity in certain cases of erectile dysfunction. Whether or not clamping and other girth exercises affect the elasticity of the tunica albuginea is now the most relevant question.
Thanks again bohm.