I have a couple of 2" EBJDs and several 3-4" sevs in a 120g growout. They completely ignore each other, so I'd agree with everybody that you should be fine.
One way to get around the conspecific aggression problem is to get a few more sevs. Chances are that you'll have one dominant, but I haven't heard one sev killing another. Wait till they pair up (if that's what you want), then save the pair and get rid of the rest.