Yeah, I can see a problem with aerodynamics...and pickup trucks.
Anyway, Roger did some older writeups here: http://www.bushwalking.org.au/FAQ/DIY_RNCTents.htm
Pretty good stuff. He will no doubt be expensive on the order of Stephenson's...not my place to say more. The 2 and three hoop designs do look pretty good for silnylon. With cuben, the angles will create problems as Ryan mentioned.
Again, cuben is actually a plastic film, like a plastic drop cloth, but reinforced with high strengh fibers. The fibers don't give much and create a mesh (asymetrical) that needs attention to bonding and force flow modeling to design properly. Small tarps/tents that you see on the market right now, are not really well engineered to take advantage of the materials strength properties. Hikers tend to get locked into a design without a lot of seams, but (again, as Ryan says) the seams need to be oriented with the mesh in the cuben directing the strength to pole "pockets", stake down points and guyout attachments. Sewing AND bonding seams results in seams that are as strong or STRONGER than the material.
Example: A fair off hand modeling scheme would be to orient the cuben fibers diagonaly...say 4 panels on a square tarp. This would allow the seaming to pick up any stake loading/pole loading. Better than common designs out now but quite wastefull of time spent sewing and stitching. This by-guess and by-gosh engineering will cover the worst of the cuben's tendency to rip loose like in Ryan's picture above. But most cuben fabric is asymetric, having more strength on one direction than the other. When forming sails, they overlay fibers in the direction of the stresses and laminate the entire sail at once. Not something a home or cottage manufacturer could easily do.