I'm 1 for 3 with the Meermin Hiro last.
Normally a US 11 D, I first ordered chukkas in a UK 10. A little too short.
Ordered some more in a UK 10.5. A little roomy but OK with insole inserts.
Thinking I'd found my Hiro size, I ordered some PTBs, again in a UK 10.5. They look as if they're almost half an inch longer than the chukkas strangely. (Maybe like a third of an inch.) Just enough to look a little awkward to my eye. Not confident sizing down would work though.