Here is a little tip about cranes if you have never used one. Always avoid two blocking when lowering or raising the boom or extending it out. What is that you ask? Well, when raising the boom or extending it out, it can pull up the block that has the working hook on it up very tight against the tip or end of the boom, and actually break the cable which will drop the block and hook even when you have a load on it, or cause other serious damage. You always have to let out the lower block with the hook on it out while you are raising the boom or extending it out so that does not happen. Maby some more experienced crane operators can explain it better then me, but from what I have read, it is the 2nd most cause of crane accidents, after tipping over, and before electrocution.
And I have seen crane operators think that just because thier crane is max rated at say 20 tons, they can stick the boom all the way straight out and lift 20 tons! NOT! The crane is rated at the 20 tons at very specific boom lengths and angles. The farther out the boom is extended, and the closer the angle is to straight out and 0 degrees, the less it will lift. One crane I have been looking at buying is an older Galion military surplus rated at 10 tons. But when the boom is extended out to 40 feet and at a 0 degree angle it is only rated at 400 lbs!
So all those charts and angles and load rating specs are there for a good reason folks!