when I'm rowing directly downwind, and the boat swings past dead down wind. For a split second, I get a perfect 'squint', and the main and mizzen don't align. But when I get back, I look at all those turnbuckles,... and well, I can't see it from the cockpit,...

It's my affliction, not the boats. I line up and sight building corners to compare their 'plumb-ness', as I walk streets. Rockort, NYC, some are always out of plumb. That's life.