OK Gang - did some more testing this weekend. The polarity swap for the tweeter (360 CD) was indeed necessary, see below.
The graph below is after I swapped the polarity on the RF (GOLD), as compared to the LF (Blue) that had not yet been changed:
The following is an even better comparison of the LF before (BLUE), and after (RED) swapping the polarity
And then some more investigation of the LF roll-off for the mains, and why Audyssey is crossing my mains over at 150Hz.
As per Tux's recommendation; I did a close MIC measurement of the deltalight II woofer, here is the result, 1" from the dustcap for both the LF and RF.
So with the my front SEOS mains behaving well; I have to assume that my roll-off is related to my room, mains placement, and/or room treatment related...?
Probably time to take this to the "acoustical treatment thread" or the "simplified Audyssey thread"