I weighed the mast end of my shop crane to determine its moment and made up a table of the equivalent hook loads for the boom extension settings. Of course if it does tip forward the horizontal moment at the hook increases, so iffy loads aren't raised any more than necessary to block them up and roll the legs underneath. If they have to be moved while raised, like unloading a truck, I chain them to the mast to keep them from swinging forward.
Cheap accident insurance:
Rebuilding a neighbor's old Curtis snow plow became much easier when I brought over my lifting gear to align the pivot pin holes. Otherwise they need about three husky guys with 6' crowbars to reassemble. I can understand why the previous owner gave it away.
-jsw