I used to be able to put my rear wheel drive Suzuki ATV on my trailer in a similar fashion. I'd pull it up into a slow wheelie as I approached the trailer, drop the front wheels on the bed of the trailer, and gas it a little while using forward momentum to get the rear wheels to climb on the trailer. It worked slickly.
One day, while showing off in front of my future wife and father-in-law, I did it with a bit to much enthusiasm, crashed through the front of the trailer and ended up on top of my hatchback car. That was my last time using that technique. I'm amazed that she still married me...
_________________________
"Mischief Managed"
2000 Regal 2550 LSC
7.4 MPI Bravo 3