I too went with opposing subs in opposite corners a little offset from a true center corner placement to wipe out the null spot (Crazy huge with both subs upfront in a L/R configuration). I noted you said you adjusted one sub up at the sub control to get the Bass you wanted. It is recommended you do these post Audyssey adjustments via AVR control. Not sub.... Just saying.
I agree with what you say regarding the post-calibration adjustments, Srattle. However, Pete's second sub is a different animal (the Hsu Mid-Bass Module), and must be tuned to exclude frequencies below ~50Hz. AFAIK, there is no way to do this in the AVR.