I remember going to a bike show at the Saginaw Civic Area back in '95 and the brand new Buell S1 Lightning had just come out for model year '96.
At that show they had bike lifts and I was impressed, but they wanted over $400 a piece for them. That was way more than I wanted to spend. I spent a Saturday afternoon at work and made one up for myself.
Mine is very similar to the ones you guys have shown.
I wasn't using mine for one winter and my neighbor borrowed it to pull his tractor apart. He figured he ad about 1500# on it while it was holding up his tractor front end while he removed the transmission.
I never did add my safety rod like you guys have, but I really never had a problem. I did have one jack that gave out on my and I used a 2x4 blocking the lift arm from falling slowly. If I think of it I'll post a picture of it, but it looks like crap after being used for the past 18 years or so.
I like the sliding outrigger legs walnutbear did with his for a bit more stability. Both jacks look awesome...