Will,

The forestay only holds the mast up until you raise the jib. The shrouds will not be tight until you tighten the jib halyard. The jib luff wire then becomes the forestay and the forestay is no longer in use. There is a small block on the jib halyard that allows you to loop around the cheek block under the jib cleat on the mast. That gives you a mechanical advantage to tighten the halyard. I believe most people keep the shrouds at the lowest hole in the adjusters to provide a lot of mast rake. If the shrouds are worn or have broken wires they should be replaced.

Howard