One of my favorites
This shoe seems to fit my foot like its painted on. I tried the solutions first but it seemed liked no matter how far I downsized I still had deadspace around the outside of my heels. Not a problem with this shoe. Its incredibly comfortable even sized aggressively. The P3 technology is great at keeping the shoes down turned shape unlike its lace up sibling which flattens significantly over time.
I wear a size 42.5 street show (New Balance 574) 43 (Nike running) and got these 2 sizes down at a snug 40.5. The breakin period was fairly short and it doesn't feel like its stretched much maybe a half size feels great for bouldering can be a touch tight for vertical lead would probably got with a 41 for more sport climbing specific fit. My foot is normal to slightly wide in the toe box, slightly high volume, with a normal heel.