Here's the rig our quail guides use, little fancy (boxes and truck bed Aluminum) but you could do the same thing or use steel to make it. Instead of tie downs for the Ranger he has a bar in front and a pivot one on the back that wedges the UTV in place on the trailer, you can see the post for the back one above the tail light.
That's like 50-Gs in dog boxes there...
... Having hog dogs in a rig like that is like wearing camo when you go hunting.