I have 2 of these and both are over 21'. I have a 20' tandem axle trailer with double lift gates with a space in the center, not 1 solid gate. I hauled ours with the arm straight up and strapped the upper arm of the pole to the lift ramp. Keep in mind legal haul height in SC is 13'6". Any low hanging lines or limbs could create an issue. Also had to put a 6x6 piece under it so the arm piece that sticks out the back wouldn't be stabbing the trailer deck. You can tilt it a little to reduce height, but the key here is the space between the 2 lift ramps.
