There was a few threads about this a while ago and there was no definite answer. Well, yesterday I finally replaced my 'rings and fitted deore middle and inner. It works fine for the middle but you need some spacers for the inner. It caused some issues with my DRS but that's easily solved too.
I just thought it was worth a post in case anyone was still wondering whether you could or couldn't, it's coming up to that season after all. I took some photos, mainly of the issues I had with the DRS if anyone wants: HERE!