Using the aerial as a highpoint anchor works well in many situations, but like others have said, using the aerial as a crane is not a good idea, kind of like never using a cable winch to raise a victim from a h***! Unless you can actually see what you are raising, the guy at the controls has no way to tell if the load gets snagged or hung up. I have heard others say, "we use voice commands to assist the raise" this only works if the guy running the controls has the ability to simultaneously hear the voice command and stop the operations. I don't know many folks who can do that, so by the time the controller hears the voice command how much farther has the system been moved
Probably the most efficient way to use the aerial as a highpoint anchor is to rig the main and belay at the designated point (refer to manufacturer) at ground level, raise the aerial device into position while extending the rope system. Once you have the highpoint in place, leave it there and rely on the rope system that you have set-up. Once the rope system has been used to raise the victim out of whatever predicament they may be in it is okay to use the side to side motion of the aerial in order to place the victim in a set down spot. When doing so I would still use the rope system to lower that victim to the ground, including a tag line system to keep the victim from swaying around i the basket.