Nice looking setup, too bad they aren't getting along.  I have only one in my tank with a couple of rays, a dynamic red aro, two tinfoil barbs and a severum.  He hasn't hit any one yet but I have noticed him chasing the tinfoil barbs a couple of times.  
Is there much of a risk of him hitting the aro?  I lost an RTG that was with three pbass and I don't want to repeat the experience.  The aro is about a foot and the IT is about 10".