Saw a company, on www, that makes a cf roll cage for the Porsche 997. theirs was designed with FEA software and is TUV certified.
It is all straight tubes with lug connectors that are molded cf.
I’m thinking machined aluminum lugs may work.
I think if anyone can make a cf cage for a car it could be someone here.
Think lugs would be bladder molded or molded over eps then the eps melted out?
http://www.2009gtr.com/2009/03/carbon-fiber-roll-cage.html
… and Cesna’s version
http://www.tomsaircraft.com/udocs/20071228154438_CAC7015C_SafetyByDesign4.pdf