Re: Santana 525 Main Halyard issue
The 525 has a pretty light stick. Have you considered dropping it? I'd recommend doing that the first time (before climbing) so that you can safely inspect all standing rigging and sheaves.
If the sheave will only fit thinner line then I'd splice double braid to amsteel instead of running wire to rope. Amsteel is just as strong, low stretch, the splice is easier, and it weighs a lot less.
1986 Pearson 28-2 "Elena"