The reason caps had been able to shrink in size is do in part to over etching the aluminum foil to increase its surface area. When you do that, less foil is needed and the body of the cap can shrink. Up until recently, when compared to their larger cap brethren, the smaller etched aluminum cap did not sound as good. I tried this experiment with the same manufacturers cap, just different case size. It was missing the relaxed quality of the larger cap. Note that both caps had been broken in. Although caps now still vary sonically from manufacturer to manufacturer, I believe the days of over etching the aluminum are over especially if the cap is designed for audio applications. You will note that caps designed for audio applications are usually a bit larger in case size for the same value.
