My size 8 in TB Revas are very comfortable yet my size 39 (US 8.5) MbyMJ mouse flats are a bit snug. It could be because they are pony hair & don't stretch as much as leather, but I would go a full size up. Good luck
at least .5 size up. I got a pair of Marc Jacobs ballet flats in my TTS and after a couple of days, the smaller foot fits fine, but my larger one still aches a bit. I could have used a half size bigger and am still hoping that the right shoe will stretch a wee bit so my big toe doesn't hurt as much.