Working elasticity on wire rope

[seawolf]

Hello all,
Here is a question I could use some help on.
I am changing all the 1x19 wire on my old gang. I am using the old wire as a template. The rig was in tune with the old wire. And measurements will be made with the orginal turnbuckle settings while the rig was in tune.
Question:
Since the rig was in tune, can I assume that the old wire was cut to size with the working elasticity computed in, and that I will not have to worry about this computation if I match the wire lengths exactly?

Wire is 1X19 SS, 7/32 dia. and the longest wire is the backstay at approximately 35 feet.
Cap shrouds approximately 30 feet.
Any feed back appreciated.
Seawolf