Nice score Nelson
I remember you said you wanted one a few years back, and now you finally found one. Google up Sky Hook, you can get lots of idea,s from the site. They use weights, and on some of there setups they have out riggers to prevent the load from toppling over. Looks like out riggers would do for you. You might look at the bases they sell too. It could be handy when you don't have the room for the base you have now. My sky hook is used mostly bolted down to the lathe, or mill. But I do have a hydraulic lift cart that I nail it down to aswell. I usually bolt it to the cart when removing very heavy items from the trunk of my car.
Enjoy, your going to love that little crane. You got a great price too.