[reichman]

Thanks for the input everyone. I made some progress, but this won't be the last post from me in this thread.

I'm using Dolby Audio Bridge, so all the Pro Tools audio goes to the Renderer, and the Renderer does a 5.1 downmix. Dolby suggested I change the downmix algorithm in prefs, and switching to "Direct Render" makes my objects perform the way I expect them to. Problem solved! Except, the beds don't behave as expected in this mode. They leak audio into the front no matter how far back you pan them. So...

I switched to old-fashioned Send/Return mode. This is a more complex setup, but it has a significant benefit: I can leave the Renderer in pure 7.1.4 mode, let the audio return to Pro Tools, and then Pro Tools can do the downmix to 5.1. This is much better, the objects and beds behave the same way. No restrictions, no leakage.

The bummer is that Dolby Audio Bridge should be equivalent to a virtual RMU. But either I'm doing something wrong, or it it still has some bugs to work out.