I second this statement, but both me and a buddy of mine have the MM PHB on our cars (my GT and his Mach 1) with a SLP LM2 catback and have no problems. It took a little adjusting here and there, but the SLP system is in several parts, so it can be adjusted enough to clear the PHB with no issues. My Magnaflow system had no chance without major tailpipe modification.
I have the SLP LM1 and saw where the SLP tips may fit. Just wondering if real world had done this or if it was interwebz talk.