To honestly answer your question about the crane, I think if you are not sure exactly what you need, then you should rent more, until you are sure.
Renting is only a small amount more expensive than owning, but it's much cheaper than buying the wrong crane.
You should also ask the operator specific questions. When you rent, rent different sizes, so you can get a feel for the different size, brand and age, of the equipment and operators.
Who's going to operate your new crane?
We got a CD from our crane place that has lifting charts for all the cranes they use, that might help you to study some different lifting charts.
I hope that helps, and I'm sorry for sidetracking your thread because of that troll Lumberjack.