Do you trailer your boat? From what I understand the stock setup is less likely to kink the shrouds vs. turnbuckles when raising and lowering the mast.
Do you race the boat? If so fine tuning might be a factor, but if not once you adjust the rigging it should be good for a long time.
On the load the 5/32 nd shrouds don't need even 400 lbs. on them. I might still move from 1/4 to 5/16 to just help with the ease of turning them. Another thing to worry about with the turnbuckles is galling and freezing. One day you might want to adjust them and find that they don't turn.
Adjusting the stock shrouds can be done very quickly without a tool if you have a mast raising system and even if you don't. Just lower the mast slightly to take the tension off and move the plates to a new hole and pull it back up and pin it and adjust the tension on the forestay and check things. Once you are happy you are done and have pretty much a non-maintenance system that has worked on thousands of boats.
Here is a cut and past from what I put on another Mac board recently. Take it for what it is worth and realize I'm not being critical of how you or anyone else sets up their rigging.
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at first we used the mast raising system to pull forward on the forestay and pin it. Then I would tighten the turnbuckle after that. I thought I had it plenty tight with proper tension on it. There was no side to side sway of the mast when sailing.
Then in Canada I was on another guys boat and noticed that his shrouds seemed to be much tighter than ours. He showed me how he would pull in on them with his hand to where they would come in about 1 1/2 inches under moderate to heavy pull. The next time the boat was on the trailer I lowered the mast and then adjusted the shroud chainplates to tighten the forestay further and ran that way at Lake Powell.
Then I wanted to make up all new standing rigging for the boat before we went to Florida. I had a forestay made up by rigging only as I needed a swagged end for the turnbuckle, but made up all the rest of the rigging myself. At the same time we bought a loos gauge and used it when I rigged the boat. Using it I found that the rigging still could be quite a bit tighter and rigged it that way using the new Johnson lever and headstay for the furler. I really like the way it feels now. If you go forward on the boat and grab the shrouds they hardly move at all.
Now we use the mast rasing system and pull very hard using the winch to just pin the forestay with the Johnson lever un-done. Then it is pretty hard to snap it over center and pin it. Now the forestay is a lot tighter than when I pinned it and then turned the turnbuckle.
The moral of the story is that I'll bet most of the rigging out there is not near as taught as if you bought and used a loos gauge to set it up. I also doubt now that you can get a really tight rig by just using the winch, or pulling on the forestay and pinning it. Will your rigging fail. Probably not as we and others have done this for some time.
I've been trying to think of some easy way we could share a loos gauge between us that would work. If you ever get the chance use one and see how tight the forestay and shrouds are on your boat. I think you will be surprised by what you find. Ours is now over 300 lbs. Can you pull that hard?
I'm certainly not trying to tell anyone on here how to rig their boat. Most of you have been sailing way longer than us.
When we bought the boat we had to read and learn everything on our own and one of the things I worried about was how tight should the rigging be and was I over-tightening it with the turnbuckle on the forestay. Well as you can see from my other post I was a long ways from having it too tight. That info might help someone else like us that maybe worried.
When we had the new forestay made up we went from 1/8th to 5/32nds (personal choice). I also went to the next larger size Johnson Lever than what most use and all of the rest of the fittings associated with the forestay have also all been increased in size so there is no one weak link.
According to the table here....
http://www.loosnaples.com/how-to-use-90-91
1/8th on the forestay can be 320# and 5/32nd on the forestay can be 500#
and on the shrouds 5/32nd can be 350
If I remember right I have the forestay a little over 300# now and the shrouds around the 350 number. Right now I'm way under on what could be on the forestay with the 5/32. I was going to increase the backstay to 5/32nd, but then figured that wasn't really necessary on our boats since the backstay doesn't do much in the way of taking big loads so made up a new 1/8th inch one.
Since we tend to stay out for long periods we can't pick weather days and never know what we might end up with. That was the reasoning behind increasing the forestay. We are cruisers and aren't that concerned with performance, so now have more of weight aloft with the little heavier forestay. We still have the old forestay attached under and inside of the new one on the mast so that it can be pinned behind the furler and our old hankon sails used if needed. Also if we get one we could run a storm jib up the old forestay. We also have a topping lift in the back and a separate anchor sail halyard and now the VHF antenna at the top of the mast. To tell you the truth we aren't good enough to feel the difference of more weight aloft vs. when we first sailed the boat.
We now sit about 1 1/2 to 2 inches deeper in the water with the new mods and loaded with water/fuel and food for a month. We can tell the difference there and it has seemed to of stiffened the boat up as a lot of that weight is down low in the hull. So for us that has been a good change.
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Good luck,
Sum
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