Initial
http://members.toast.net/schwingding/initial.jpg

corrected
http://members.toast.net/schwingding/corrected.jpg

The BFD filters don't extend down past 20Hz, nor does the onboard PEQ on my dual PB12+/2s. Don't know what I can do about that hump from 15-18Hz (but am glad I have power down there), don't want to add gain using the BFD either, right? Any suggestions - I have substantial room treatments but no real bass traps.

You will find a great deal of help regarding using the BFD effectively at Home Theater Shack.

Is that your sub only or did you have one of your mains playing as well? If that is sub only, you should play one of your mains as well to see how well both integrate, you may be messing things up down by your crossover and not realize it.

Nice graph by the way :)