That sounds fine. Lucky grey gets lots of room. I will say there are a small number of greys that do not like all the extra room. My grey is one of them. I got a macaw size for him and he hide in the corner and never came out. I down sized to what he has now and he is happy. (I would love to see him in a bigger cage!) All I can say if you already have the cage is try it out! You may ask the owner what size he had at home.
I think it should be fine, I have Rosie in a cage with 1" bar spacing and she for sure can't get her head through. The vet always comments how she has such a petite head too, and kenji's skull is way bigger than hers so a CAG should have no problem.