I will get some better pictures of the car and trailer posted, but the scaffolds are interior
baker style that when loaded on the trailer make a box about six and a half ft long, three feet wide, and about eight inches tall. I've strongly considered an extremely small swivel wheel system that would only hold scaffolds, but I often have to carry a minor amount of material, or other equipment that won't easily fit in the back seat. The trunk is always filled with tools, and some of them will live in the trailer, as well as a ladder, push brooms etc when it's completed.
I've been using this car/trailer combo exclusively for almost 4 years, and with normal driving does pretty well. I've never had the opportunity to compare full tanks with and without the trailer, but I'm guessing it robs around ten percent when loaded. A real world comparison that comes to mind is on a vacation trip with the wife, I was able to (no trailer, car was empty, and by the cars info) drive at an average of 70 MPH for an hour and it read 40.1 MPG, and on an hour and a quarter drive to a job (three adults, trunk crammed with tools, trailer with three scaffolds) drive at an average speed of 66 MPH at 37 MPG. I've tried recreating the loaded scenario and have come within a couple of MPGs, but I suspect the loading of the scaffolds just happened to be perfect for drag that day, or just a good tailwind lol.