I only do that size-down-half move if:
1) I buy the shoes in E width
2) I plan on wearing them with thin or no socks
That's me personally. I wear size 10 in most sneakers, 9.5 in Alden Indys, etc. and 10 in almost all Yuketens with the exceptions listed above. I have Country Rangers in size 10D and they don't feel very snug (and they're too new to have stretched yet). That's my experience.
I definitely shouldn't have sized down, but I saw a few sources saying I should and 11s weren't in stock (I'm 11D for just about everything, a bit on the wider side). My first online shoe buying blunder, hopefully I've learned my lesson. Have your other yuketens stretched much (assuming you have any in a similar type of leather)?