I plan to use Dyform wire and Hayn Hi-Mod compression fittings.
Meanwhile, I'd like to carry a spare wire and two compression eyes and a compression stud in case of a failure anywhere. This would work well, as all my stays have eye terminals and are connected to jaw-jaw turnbuckles ... except the head stay which has a 3/8" - 24 turnbuckle stud on the lower end.
On measuring wire sizes, thread sizes, and pin sizes, I discovered all the eyes at the end of the wires have 3/8" holes. At the top of the shrouds/stays there is a corresponding tang or toggle with matching 3/8" pins.
However, at the bottom of the stays all the jaw-jaw turnbuckles have 5/16" holes and 5/16" pins through the 3/8" eyes.
The lower end of the turnbuckle is pinned to the chainplate, which is a 5/16" rod bent in a loop. (See picture).

My dilema is whether to up-size my turnbuckles to 3/8" pins to match the 3/8" eyes, or stay with 5/16" pin turnbuckles and downsize the new eyes to 5/16". Is there any sense in up-sizing when the chainplate is only 3/16"?
Also, most newer boats I see have a toggle at the bottom of the turnbuckle and a turnbuckle rod swaged at the top of the turnbuckle. Is this better than the jaw-jaw turnbuckle, or just a cheaper way to do it?
As always, I'm open to all opinions and suggestions :-)