A load will always tilt until its Center of Gravity is directly underneath the crane hook. If the CG is not balanced between the rigging points, one sling will carry more weight than the others, risking an overload.
Evaluating ground bearing pressure to ensure the crane mats and soil can support the combined weight of the crane and the load. Safe and Approved Rigging Engineering Resources
Before hunting for a PDF, you need to understand what you’re looking for. A high-quality rigging manual will cover these five essential calculations in detail.