Sizing a panting stay

[Svinshallah]

I'm positive the two breaks were due to corrosion. I replaced the broken stay with a 1/2" turnbuckle with 1/2" clevis pins at each end and 5/16" compact strand wire. My specific question was based on the fact that of the several versions of this stay that I've looked at in other boats, all but one used a solid rod that seemed much stronger than the turnbuckles or attachment points. I was curious why and what was likely to be the weak point.