I found that the #3500 jacks was a bit larger in diameter than what I had. I got the #3000 rated jack and it's been working great for 10 years now.
As far as speed goes, the faster it goes, the less weight it's going to be able to lift.. Just like trying to start off in 3rd gear from a stop light..
The one thing that bugs me is how loud the electric jack is, so running it in a quiet camp ground pretty much lets everyone know you have arrived or are leaving.. ;)
Mitch