Backstay
Split backstays can be rigged to be adjustable simpler, and easier than single backstays. Change the tension of the backstay, and therefore the the forestay tension. Tighten the backstay and you tighten the forstay. Ease it and the forestay eases. Tighten going to weather, loosen off the wind. A proper offshore rig would have two backstays from the mast head to the corners. Unless you are real anal about sail trim, it's set it and forget it.