Hand Tight
I agree with the comment that the lee sidestays will always be slightly loose. This is true for every rig style. Every sailing brochure, book, and magazine I have read on standing riggin says the same.I also agree that you do not adjust stays under sail. Your rig is loaded from one side, and any adjustment will be false.Best approach is to to your final adjustments in the water at rest, not on the trailer. In the water, the boat is uniformly supported, and the chainplates will be in their true relationship to the mast. Adjust the lengths to get plumb, side to side. My istructions for my 23 say to tighten the the turnbuckles handtight only. If you use tools to lever the turnbuckle tighter, you are preloading your standing rigging. The result over time is likely damage to the weakest part, your chainplate anchorages to the hull.