I know this thread is a bit dated but others might benefit from my experiences.
1) V-Spoilers (aka AirTabs, EcoFins) are the best retrofit I've used to stabilize my Winnebago on the road. Either two lane with opposing traffic, or 4 lane with semis come from behind. These little vortex generators nearly completely eliminated any side to side rocking or pushing by big semis passing me on the road. Wind, even blustery wind from the quarters, hardly affect the RV's stability any more. Absolutely my favorite mod to the RV. Stick them on, and arrive at my destination fresh. No more having to clench the steering wheel when I see a semi. They are available in sheets or you can buy them in singles like here on eBay:
Vortex Generators . I got them from
V-Spoilers as a promo but they were $265 a set back when I installed them. They came on sticky backed sheets of 4 per. You need like 55 individual vortex devices or so for the back of the RV. I have them installed along either side in the back and on the roof in back. I guess V-Spoilers aren't being sold in the US now, but AirTabs are and they're the same thing. Now that fuel prices have jumped, I'm going to buy the individual types and put them on the front. The ones I have calculate out to save me around 5% on fuel when I'm driving on the flat with no wind. Any other fuel savings depends on wind strength & direction of course. I'm hoping for another 2-3% when I add the new ones. But I don't care about that as much as the stability they afford. Really work well on a Class A RV like mine (see sig).
2) My other favorite mod was to add
SnapPads to the bottoms of my 8" jack landing pads. Prior to the SnapPads, 75% of the time when I'd arrive at an RV park, I had to jump out and place my wooden landing pads before dropping the jacks. Or I'd have to add them later as the RV sank and got out of level. Now, 90% of the time, I drive into a space, and just drop the jacks. Rarely anything else to do. The SnapPads broaden the footprint so less chance of punching through blacktop or sinking into moist ground. I do keep the wooden pads for those difficult parking spots.
3) Then I added HDMI cables from the entertainment cabinet up above the drivers seat to drape down along the wall behind the driver and to the passenger side so I can plug in any computer with an HDMI output into my main TV. Very cool...I have a tower computer at the dining room table and stream movies and TV using that cable. The other one is backup from my other computer but soon I'll have a TV cozy there with the 47" TV so the HDMI cable will come in handy. I ran the cables under the false bottoms of the overhead cabinets. No more unsightly cables draping from the cabinet doors.
: 
Linear Mode
