Blue,
Sorry everything takes longer than I want. Soon (a few months), we'll get to a more realistic body and start looking at diffusers, drag, but shape and front end shape.
Recently, we've been looking at devices to keep the cars from flying when they are sideways. On the very simple body, roof rails mounted the length of the body cut the lift by about 25%. Some other types of rails were more effective but would also have an effect when the car is running straight. It looks like the idea of running splitters down the side of the car (running boards) doesn't work. They seem to mess up the air flow under the car when it is sideways. In 2009 the LeMans prototype cars when to a profiled skid plate under the cars in attempt to lessen the problem of them flying when they are sideways. It looks like they cut the lift on the simple body by over a factor of 4 when it is sliding sideways. It will be a couple of weeks at least before all this analysis gets double checked, written up and published to the web site.