I think thirdman is onto something
in the first half this infomercial they show a back view of this concept SAAB
looks like it has active spoilers that extend behind the hatch and under the bumper - but they seem to indicate they are for low drag - "10% reduction"
not unlike what thirdman has shown
and I am very interested in the thirdman concept for my truck cab
but expect it may be a very tricky to get it just right
and if it is not right I'm sure it would increase drag
a Kamm back may just be more practical for those of us that don't have wind tunnels
BTW
justpassntime is building a short Kamm back - similar to matrix wing
he says it will be somewhat adjustable during development
could shed some light on this topic to have some real world data
http://ecomodder.com/forum/showthrea...bers-3945.html