[lunarhighway]

the latest mercedes e class convertible has a small wing on top of the front windshield that pops up as the roop opens, it's there to reduce wind noise, but it comes at an aero cost

where the e class coupe has a stunning 0.24 drag coeficcient for the slipperiest model, the open cabrio is said to have an 0.33 Cd, pretty good for a cabrio but this raises to 0.38 with the wing deployed.

it's not quite the same as the thing in the original post, especially since most of the body remains intact (vs a convertible) but anything like that will add drag