Nice benches-- i haven't got as slick as that. i just built a wooden box on the bottom of a round 3/4" piece of plywood, and attaced 2X4 legs angled out, and attached with wing nuts. When i set it up, i can tap out the legs, and it's "pretty" steady. i'm certainly not suggesting it over the others, in fact i'm seriously thinking of trying one of those. One thing i did do that i like is i attached some indoor/outdoor carpet to the top that keeps cartridge cases from rolling around and off the bench, and adds a good bit of comfort for the arms/elbows.
Anybody ever shoot off the back of a tailgate? I've got a rug-type bedliner in the back of my pickup, and it's about as sturdy as i've ever seen. When i remove the tailgate cable, i can get my arms in for elbow support, and there's just enuf room to make it comfortable, especially with a singleshot pistol.