Reality Check

[benz]

when you have a fat wire, it takes more force to put the correct amount of pre-tension on it. If you take an 8th-inch piece of wire, you can pull it pretty tight between your hands. Take a piece of half-inch wire, and you can't pull it hard enough by yourself to get the catenary out. So regardless of strain on your rig when sailing, getting a proper tune with undersized turnbuckles will already make them work harder. I expect those Hayn's can probably take it, but I'd be inclined to stick to the size specified for the wire in use.

If you're replacing all your shrouds, this might be a good time to consider going synthetic. It's easier than you'd think, and Colligo (no relation to me) is a one-stop-shop for all the kit you'll need.
Ben
zartmancruising.com