.5 down is enough, full would be uncomfortably tight.
Everyone's foot and comfort preference is different though. The guy above went TTS and liked it, for me there was too much room in the forefoot compared to the Lunar Chukkas.
If you can't find these in store, try on any of the recently released Chukkas with the OG Free sole. You'll be sliding all over the place with TTS or up. Sizing down is a perfect fit on these (unless you have a very wide foot).