Proper headstay tension with furling unit

[seawolf]

I typically use a gauge to tension my standing rigging. I will be installing a Harken furler in the near future and once the foils are installed, I do not see where there would be enough exposed wire to install the gauge to use for tensioning. What are the recommendations for getting the proper tension for the headstay with the furler installed?
Thanks for all the great advise.
Seawolf