At long last
Hello,
This one just fell off my radar. Thanks for reminding me that your question was lurking, far down the scroll.
The distribution that I used in the Apprentice assumes that there will occasionally be serious loads at the 3/4 height of the mast, as when the jib is furled, the forestays'l is set, the main is reefed, and the boat is driving hard to weather. In these circumstances something like the lateral load that was at the masthead is now down lower, hence the shroud sizing.
But other designers have argued that, even if there were transitory high loads here, they aren't enough to justify the larger wire size. Only a load-cell test might settle this disagreement, though it might be worth running the more detailed calculations in Larsson & Eliasson's book. For your boat, I'd say it is safe to go with the smaller wire, particularly if you don't make much use of your forestays'l.
As for calculating loads, adding weight does not always add stability; sometimes it reduces it. Best to conduct an incline test.
Fair leads,
Brion Toss
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