I've got an aluminum home-made one similar in design to the sledez. It works great, on thing i really like is that the skid don't come-off when moving it around like they alsways do with the three-dolly system.
To keep it as low as possible to the ground, I used real small casters, like 1-1/2" diameter, and they don't seem to last too long.
If ya get real good at driving on it, you can come cruising-in onto the dolly, hit the brakes, and the sled/dolly will then coast a ways.
Carefull pulling-off the dolly, too mush gas and it'll go shooting out the back.