The winglets definitely keep a lot of cold air off you. Actually, I notice them most in reverse. If it starts getting warm, I need to pull them off or I start roasting.
The madstad screen IS a huge barn door - no way around it. Definitely NOT suitable for real off roading, it moves around quite a lot (IMHO, due to the mass of the metal faring bracket and the cantilever effect of the adjustable mounts themselves) and it is tall. Gravel and dirt roads are fine.
If I'm doing anything more exciting, I pull it off, stick it in a t-shirt and bungie it to my duffel bag. Both due to the height hitting me in the face and how hot it would be at low speeds.
The only other system I would consider would be the Mirage-type set up, but that sure is pricey.
You can see it strapped on the back here: