How Much Tension on Inner Forestay?

[Brion Toss]

Hi,
Do you have aft lowers, or are they athwart the mast? The answer will affect details, but either way you will need to use your runners most of the time, because the forestay will be pulling on the mast all of the time. If you slack the forestay to eliminate this, you will get a lot of oscillation, and little hope of an effective sail. You can determine if you have correct tension by determining the amount of luff sag you have in a given windspeed/course.
If you have block-and-tackle on the runners now, please remove them; lead a single line through deck blocks to the primary winches. Much easier to use, and much more effective at tensioning that stay.
Fair leads,
Brion Toss