Ok I just went for it and they came out great. This was hot wash, cold rinse, hot dry. Used detergent even though that was obviously unnecessary. No noticeable fading or color bleed. I didn't measure before starting, but based on try-on before/after I'd estimate that they lost 1.5" in the waist, 1" in overall length, and are noticeably more snug all the way down. And my estimates are probably conservative tbh so make sure you really want a smaller pair before trying. Other than the size difference they look basically brand new. Hope this is helpful to anyone with the same issue!
EDIT: The leather tag did come out looking a bit more weathered than it went in. I like the change but be aware that it will probably happen.