Not sure if this completely the correct thread for this but....
Only difference I can see on the "Road Atlanta" Spyder (looking past the non-painted front nose) is that the raised central section of the car is different, with there being a pronounced lip to the front edge, and more of a gentle slope to the edges.
Dive planes appear to more steeply angled on the RA version too, with the loss of the lower endplate allowing them to be mounted lower.
Also, on that link jhansen has posted, if you click on development and testing, and then estoril, there is a small video of the car on track.
Regards
Ed