[COBRANIP]

DocDirk, I have the same curosity and am working (?) on a similar project but am not far enough along to shed any light. I am starting with a Herb/Matt Adams aluminum frame (200 lbs) and a FFR carbon fiber body (probably under 100 lbs). I am looking at it primarily as a track car. There is no doubt a heavy car will have a more comfortable ride (assuming a relatively heavy sprung weight to a relatively light unsprung weight...that is simple physics).
One other benefit is for any given HP/WT ratio the lighter car will require less HP... which I think can translate into a "more reliable" and less extreme engine.
The biggest problem I anticipate is traction. As you get lighter and lighter how do you get the power to the ground?
I really enjoy the engineering challenge which is my motivation.
I would think the biggest advantage would be in something like an Autocross course.