[ecomodded]

The Beetle Rsi was made for racing, it requires down force to stay on the track that's why it has the roof spoiler directing air onto the trunk spoiler so it can create the down force needed to stick the car to the road.
The Rsi's spoilers cause more drag on the cars aerodynamics but allows the car to stay on the track so it can race, A very positive trade off indeed.

The Turbo S has a single roof spoiler that auto deploys at speeds greater then 45 mph to 70 mph {depends on your setting).
It was put on the Turbo S to break the lift caused by the poor aerodynamic design of the rear of car which develops suction as speed increases.

Suction= lift =resistance=drag= less mpg
(& poor handling at speeds)
I installed my roof spoiler in a attempt to break the suction off of the rear glass to reduce lift and improve the aerodynamics of my Beetle.