Freebeard - Thanks, it's just coroplast, no aluminium skin or anything, it's a light material although difficult to shape. The second body was much easier, all done by hand, where as the first one, I had to make a jig to lay up the panels in and glue it all up.
I wasn't sure which ground clearance you were thinking of so I tried both 30mm and 100mm models. The inverted horn shape at the back does help to reduce drag quite a bit. The 100mm model gave me a slightly lower drag than the 30mm model but only by 3% despite having a much larger frontal area. Both model were about 15-17% less drag than catamaran design in permalink #9. Here's some pictures of what I did.
After this I went back to the catamaran design as I wasn't happy with the front section as I felt it was too abrupt to the airflow. I moved beginning of the side flanges much further back and rounded the front nose off as much as possible. I also made top two edges along the body to have a much bigger radius to allow the airflow to flow more easily around the corners. This gave me the lowest drag force so far, about 22% less than the original catamaran body and a drag coefficient of 0.11. I'm going to have do tests on the most of the models at 15% yaw as airflow is never going to hit the car dead on with crosswind and so on.
Aerohead - Unfortunately there's not much I can do on the rollbar, the only thing I can do is, there's been a trend lately to hide the rollbar behind the helmet to minimise the impact of it by having a very small bend radius, like I had on my previous car.
All of the rules of Greenpower can be found here, there's a section on roll bars, banning the use of fairings -
http://www.greenpower.co.uk/sites/de...ons%202016.pdf