Thinking more about it...
If the problem was hot brakes I can see those exiting fender vents improving flow past the brakes.
At the risk of sounding like Hermie, I agree that lift on a Bug can be a bad thing since they are reaching the speeds where it becomes critical. And in any circumstance, a body that creates lift is also creating drag.
Re: "The Fix": Agree the airdam is effective, and depicted but not labelled is the lowered suspension, also effective.
I have my doubts about the fenders causing lift and especially if they do, that those vents are a cure. I wonder if manometer readings on the outside AND inside of the back of the fenders would show low pressure? I speculate such because the flow past the wheelwell opening should be causing a low pressure on the inside- in the wheelwell- and the flow having to tuck in aft of the fender should also cause a low pressure on the outside- between the wheelwell and the door. I think both of those effect the drag component more than the lift. But I don't know.
I was thinking about why the top-of-the-rear-window spoilers seem to be more popular than the "Herold's (sic) Helper" style, below-the-rear-window spoilers. I'm confident the Herrod's have lower drag but I suppose the "top style" is better at reducing lift because it is more out in undisturbed flow, for the same reasons the Dodge Daytonas have their wings so high up.
That raised hood on "The Fix" made me laugh.
