The VIS invader hood has a large vent across the front. now if the engine bay gets air from underneath and it rushes up into the bay towards the top, wouldnt it continue thru the vent and out towars the back creating a good amount of downforce at higher speeds? this is what the hood looks like...

 

Even if it did put some downforce over the front wheels (i doub it) at real high speeds, you'd be moving fast enough where traction really wouldn't be an issue I would think.

 

just put a big GT style metal wing on the front of your car.

 

As much as people bitch about them, canards make a NOTICABLE difference at anything above 70 mph. Nothing will beat a properly designed airdam though.

 

It won't so much increase downforce, is it will reduce lift.

Most street cars have a decent amount of lift at speed; your going to need a bit of solid aero work to even start making downforce.

A hood like this will help decrease the lift a LITTLE bit, because you don't have as much turbulent hot air going under the car. However, the difference isn't enough to worry about too much on its own.