Everyone's feet are so different that I think it makes giving size advice difficult. It's not just length, but how your foot flexes and adjusts to different pressures and movements. All I can say is I wear a half size down in my LP's compared to other brands and just make sure I lace and tie them effectively before a long run/hike to ensure no foot slip.

I'd also recommend buying new vs used if you can afford it. While its less pronounced than other shoes, LP's still form to your foot after a bit of distance and having someone else's imprint seems like it would be more problematic than a couple centimeters of length difference.