Good points, all. As mentioned, I've only jacked the back of the truck with the hi-lift once, and that was only for about 30 minutes to swap out my rear shackles.

I definitely did not dare crawl under the truck to work (you can do the shackles from behind the bumper). Also, I'm always leary of a jacked vehicle moving in any direction, so I was sure that the front wheels were chocked front and rear.

This was on my level driveway, too. I agree with TJ - if I were out on the trial on an uneven (and worse yet - loose) surface, this probably wouldn't be an option unless it meant the difference between something positive and something very negative.