Smaller rear wing should make no difference. It's a stupid idea I think.You just run a thicker chord over the aerofoil and at a higher alpha to achieve the same downforce. The only issue is, running at a smaller span, you reduce aspect ratio and you will make the wing less efficient. i.e. from a smaller wing you will get more lift induced drag and stronger wing vortices - disturbing the airflow more.
I know one concept looked at is this:
http://www.fia.com/resources/images/...DG_graphic.jpg
I can't be bothered to state the FIA's massive oversight there though.
The fact is, F1 cars are not aerodynamically efficient. My SEAT Ibizia, my Dads Honda Accord, heck basically everyones car has a lower drag coefficient than a Formula 1 car.
Why? Because they are opened wheel. Circles create massive, horribly alternating vortices off the trailing edge. They are the source for most the drag and most the
turbulent air. Nothing to do with rear wings. I hope FIA realise this and allow proper wings on the back for 2010.