971's chassis

[cxcad]

This year I think 971 has built one of the most effective and innovative chassis, and consequently I want to emulate what they have done.

I noticed from the Flikr account that this year 971 departed from from what I presume the "original" three piece design. Could the octagonal shape not be achieved in three pieces? (image here)
That brings the questions: do the ribs provide significant rigidity?
What's the advantage of one piece modules over the traditional railed approach? (image [I know there are ribs inside it, but for the most part it is one piece?])
What is the advantage of PEM nuts, is there a closer image of them in use, how do they hold up to the beatings and vibration? (image)
Finally, what are those giant copper type plugs?