New size mast how to measure for rigging

[grboregon]

Beneteau Oceanis 41.1. Bought it with a missing mast and rigging. Came with a new Soromap mast, boom, but no rigging. I am apparently in my dumb mode as I am not sure as to how to go about measuring for the standing rigging while mast is down. Seems like stepping the mast with no means to hold it steady is not an option. So help me out I need to be educated. Boat is lying in St. Maarten. I am in process of doing a major refit as the boat was vandalized after Irma. No hurricane damage, just theft. I am comfortable with redoing wiring, plumbing, etc. but the rigging has me questioning how to go about it. Trying to avoid the expensive riggers in the area. Want to get it up, then pay to have it tuned. Thanks in advance for your help