Well, I'm not about to do anything really radical to the family van, but tonight I completed my first aero mod to our 2001 Honday Odyssey van.
Before:
After:
No more roof rack crossbars!. I think we used it maybe once as designed in six+ years, so it's just wasting gas 99.999% of the time. Probably not a lot of frontal area reduced, but I'm confident it will help at least a little, and it only took a few minutes to do. Not only does this reduce drag, but it also removes 10 pounds or so of unneeded weight.
We've only been getting about 16 mpg in this van with all of the really short trips it does, but maybe this will give us 0.5 to 1.0 mgp improvement? We hope we detect some difference!
I'm leaving the side rails. They don't have much frontal area, are fairly smooth, and would be a pain to reinstall I think if I do need to use the rack sometime.