I have stood branches up before like you speak of, but always well within the chart. I could see a potential danger doing that with a big pick. As you stand up a piece, it has the potential to swing, therefore the pick could swing itself out of the chart. If it was bad enough, it could flip the crane. I remember a write up about the guys who flipped a 40T because they only slung the trunk on one side so it swung out of the chart, and they split the house with the boom. Because of the swing, not standing the piece up. So again, I think as long as you have the chart, and the room to spare, should be OK.
Personally, I like to balance as well as possible. Spider legs or multiple slings.