When I recovered our XM818 I flat-towed it 130 miles from Midland, TX back home to San Angelo, TX using our Deuce as a tow vehicle.
(The whole story is in the link below in my signature block if you'd like to read the details.
You MUST READ Post #76 in that thread before attempting your flat-tow!!!)
The recover was a success, however, I will NEVER again do that. The 13,500# Deuce was too light for the 19,000# XM818 even with 1000+ lbs of ballast in the back over the drive axles.
PLEASE be absolutely sure that your tow vehicle is HEAVIER and has MORE TRACTION on its back end than the towed vehicle has on its front end to avert DISASTER.
DO NOT tie down the steering when flat-towing.... unless you are trying have a crash. The towed vehicle's steer axle MUST be allowed to follow the lead vehicle's direction of travel. PERIOD ! ! !