Yeah, I wouldn't do ATL-SJU-SXM either. Maybe ATL-SXM, but definitely not with the extra SJU stop. Both DL and UA are routing pax through SJU on some days, using Seaborn (now part of Silver, I think) as their SJU-SXM carrier. It's quite a hike to the Seaborn gates in SJU Terminal D.