Measuring new rigging from scratch

[glowell]

I am rebuilding a 47' mast from scratch using pieces of the old mast as a guide. I hope to get it close but there will be some size differences. How do I get an accurate measurement for new standing rigging? The only way I can see is to launch the boat, step the mast and test the length using the old rigging, then adjust from there. This will require stepping and unstepping the mast a few time, a lot of crane time. Just wanted to see if there is an easier way, Thanks Gary