Growing up we flat towed our 40 behind a F150 with no issue. I flat towed the 40 from Sacramento to Seattle behind a uhual box truck, with not issue. I have flat towed the 40 behind a 2005 tundra on the interstate and highways with no issue. The only time I had an issue was flat towing the 40 behind my tundra on a logging road with an inch of fresh snow. That scared the hell out of me. I could not stop the truck and was being pushed down the road. Once I got back on pavement, no issue. I would not hesitate to flat tow my 40 on the highway or interstate again. I would only be concerned with poor road conditions. I keep it under 55mph, and have plenty of space for braking.
If nothing else, flat tow the 40 as much as you can. If you have to, disconnect from the tow vehicle and drive through the area of concern. Good luck, be safe.
If nothing else, flat tow the 40 as much as you can. If you have to, disconnect from the tow vehicle and drive through the area of concern. Good luck, be safe.