I went TTS on my pair and they are a bit roomy. I think I could've sized down, but I also have a pretty low instep. If you have a normal/high instep you might be alright. I'm size D and I found them to be quite wide as well.
Do you all notice a difference in size between monks and oxfords? The rain last only just works with my low instep and I've been reluctant to get monks because I'm afraid they'll be looser than my lace-ups.