Bestway
To replace your fore stay try this.Take a 1/4" line and a small block and tackle.Rig the top end of your replacement fore stay and attach it to the mast. Leave the bottom end a little long with no fittings. Run your jib halyard through its pully and tie off the free end to the halyard cleat on the mast. Attach your aft stay in the normal manner and at its regular adjustment (if unknown connect it half way in the slide). Adjust your fore stay turnbuckle to its midpoint and attach to the forward hole in the stay plate at the bow of the boat. With your side stays attached, tie the jib halyard to one end of the block and tackle. Attach the other end of the block and tackle to the aft hole on the stay plate. Raise the mast and use the block and tackle to remove any slack from the rigging and act as a temporary forestay. Tie off the block and tackle. Have a friend pull the center of the halyard/block line toward the trunk of the mast until the all rigging is tight. Pull the new forestay wire down to the turnbuckle and mark for the fitting. Take it all down and install the fitting on the fore stay. Shorten the mark a little to make a small allowance as the forestay will straighten some as it looses the "set" of being wound on the spool. How much will have to be a judgement call, is the new wire kinky or really straight?Rig up as normal. As far as a fixed measurement I don't tend to trust them too much. If your boat has had a replacement mast or the foot of the mast has been trimmed due to damage a fixed length might not do you much good.Good luck,Mike