Reality Check

[JohnV]

In the midst of planning replacement standing rigging, I’ve learned why it’s important to size turnbuckles at about 4/3 the breaking strength of the wire.
My heavy 33’ cruiser’s original cutter rig is somewhat over-sized.
Best I can learn, without doing a test (on the hard) the RM is somewhere from 20,000 lbs.(Selden’s online calculator) to the high 20’s (Apprentice, pg 136.) So to assume 25,000 lbs, and using the calculations in the Apprentice, I’d need breaking strengths of 7908 for the uppers and 5711 each for the 4 lowers. Well within the limits for 5/16” wire, but I’ll stay with it anyway.
Turnbuckles that are proportionately stronger than 5/16" wire would have 5/8” screws. But since the wires are so robust, I’m thinking I can do with 1/2” screws, like the original Navtecs have.
I emailed Hayn to ask about breaking strength of their 1/2” T/Bs. Their answer, twice, was only that it “exceeds” the #11,125 breaking strength of 5/16” wire (I though it was around #10,600, but that aside for now). I’d go with a brand with better info available, except for the high praise for Hayn from Brion T.
So: First, is it reasonable to use T/B’s of less than 4/3 the strength of wire that’s oversized to begin with?
And second, am I unreasonable to expect a more specific answer from Hayn’s sales engineer in Connecticut?
And another one--are T/Bs with T-toggles better/worse than those with eye-toggles? (I'll use swageless fittings.)
Thanks again for looking at this. I’m new at this stuff.