The vertical piece works, looks ugly but works. Here is how.
There is something called "flow seperation" which you do not want to happen before the air leaves the wing, so more surface area helps the air to stay attached longer.
Second, as they have learned in WRC, is that when you turn, especialy medium speed sharper turn, the wing unloads because the angle the air hits the wing changes gradualy with the turn, until you get straight again. So having these vertical sections, keeps the profile of the wing bigger when air is hitting it from the sides.
I think that specific application is overkill, cause a car like th MR2 wouldnt see those extreme approach angles like WRC car.
Most LMP cars have a vertical fin on either side going to the body, much like the one on DavidV's car, which works great.
They are called endplates, and the bigger these endplates are the more effective the wing becomes. I've read some equations that an endplate can increase the relative length of the wing by more than 30%, that means that in order to the same work without the endplates, the wing would have needed to be 30% longer...that is quite substantial.
T
