I'm not sure if its a contradictory condition, or just one that can't be defined in creo. As I calculate it, the beam model would have 1 rotational degrees of freedom (fixed to WCS) around its axis, and translational DOF would be fixed to both points. I could fix that one rotational DOF to one of the points to get rid of it.
Regardless, I think I may have found an acceptable solution. I have the beam fixed to the pipe and all rotation released at the HSS. I had to insert an extra constraint on the pipe to lock both horizontal rotations, but that keeps the beam element vertical. It would have been ideal if I could have put that constraint directly on the beam, but at least this is something I can alter in AutoPIPE for a good comparison.
Thanks Shaun!