If lead height is between 1/2 and 3/4 and only two or 3 spans are involved, head guys for cable should be one strand larger.

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When you’re designing a guyed cable, the forces in each guy depend on the geometry of the run. The head guy carries a larger share of the horizontal tension when the lead height sits in the mid-range (about half to three-quarters of the span) and the installation uses only two or three spans. In that setup, the load path concentrates more force into the head guy, so giving it a bit more strength helps keep the tension within safe limits and maintains balanced loading across the spans. Increasing the head guy by one strand provides the needed extra capacity without overdoing it. Using equal size would underprotect the head guy, while making it two strands larger adds unnecessary stiffness and cost; making it smaller would reduce strength and risk overloading the support.