I don't have a picture so I'll have to describe the scenario: I wasn't even really hypermiling. I was doing 57 (the prevailing speed) in a 55 zone in two way traffic on US 61 in the company truck on my way home from an incident at the flood disaster area in Oakville IA when a semi pulling a sea container decided to draft me at about 8 feet. I gestured with my open hand in the back window for the driver to back off, so he pulled up to 5(?) feet. Since I wanted to be going slow if I got run off the road, I slowed my speed to about 40 and he got closer yet. Then the "good" part, I wanted to get his license number from the plate in his windshield so I reached for my clipboard and pen. He saw me, reached over and flipped his plate down. That got me worried what he would do next, so I flipped open my cell phone, showed it to him in the back window and pretended to dial and talk. He backed off a little then and I increased my speed back to 55. About a mile later he passed me on the double yellow in the middle of a major highway intersection. His door decal with company name, ICC # etc. were too faded to be sure whose truck it was but it bore a resemblance to "Proficient Transport." [Mods should feel free to delete that last sentence]. His trailer had Maine plates, but I suppose sea container trailers are hard to track back to individual drivers. Anyhow, when I passed him an hour later as he was exiting on I280, his license plate was back in the window.