I have the 3500 model which is plenty for the Cobra, and I use it on my 2011 Mustang GT.
The larger units weigh a lot which is why I went with the smaller unit.
Yes I work under it, but I don't do a lot of heavy work that shoves the car around. More like
oil changes and small adjustments. I wouldn't remove a transmission or something similar without putting jack stands under it to back it up.