I've been experimenting for some time with Aero packages on different chassis / body combinations...
Tamiya Rover Mini cooper (Honestly!)
Ive tried the standard Tamia body on the Cooper and the HPI version and the HPI version is much better.
I also tried a rear wing on the Cooper body but that didnt work very well and just made the car over steer.
The Losi and TC4 chassis's have had several body shapes put 'over' them, Lotus Elise, GT40, BMW and a Ford Taurus... of all the bodies, the Taurus seems to work the best!
. I've tried several rear wings and either the HPI 'scoop' rear wing or a home made (formed from 1/4" ply) inverted aerofoil @ 15 degrees seems to work best on all the bodyshells.
I also did a little experiment with front splitters under the front of bodyshells but that didnt work very well on any bodyshell, mainly due to the fact it kept getting bent (aluminium plate) and i couldnt get consistant results.
One thing i DID find worked VERY well and made all the cars stick to the road like glue was a rear upswept undertray similar to an F1 car, sucking the air out from under the rear of the car
. This did however give me another problem to solve, it sucked any dirt / grit / debris off the track and inside the bodyshell!.
One other thing i found worked well, put the bodyshell 'down' as far as you can on its mount posts and then trim the bottom of the body till it doesnt drag on the ground.
I would love to try my 'variations' in a wind tunnel just to see how much difference they make 'scientifically'
Just my $0.10 worth....