The stock tank: 8' in diameter.
The trailer: 8'x4', with 4' high rails.
The winds: coming out of the SouthWest at about 5-10 miles per hour.
A complete stranger came up to Spouse and asked "how far do you have to drive to get that thing home?" "Ten miles", Spouse replied. "Wow. Be careful."
Spouse drove the car and trailer, white-knuckled, all the way home. He probably would have bit his nails too if he didn't have to keep both hands on the steering wheel.
Average speed before the tank started tipping and pivoting: 40 MPH.
We - and the stock tank - made it home all in one piece.
[pic: Spouse recovering from the trip]