Not sure about the rest of the world but in the U.S. when we are going to be using an attachment on a lift truck on a regular basis the machine is supposed to have a data plate reflecting the capacities of the machine with that attachment.

I have some customers that have two or three data plates on their machines because they own multiple attachments.

Yes it is great to know how to make the calculations yourself, but for liability issues. It is best to go to your dealer with your lifts model, serial number and mast numbers. Give them the info from the attachment and they can submit it to the factory and the engineers can do the calculations.

That way you and your company have minimal liability and all of the operators can know at a glance what the limits are.