Not exactly an answer to your question, but from my old copy of the FCTM, one of the criteria used by the FMC to calculate the Maximum Altitude, is the maneuver limited altitude.
"-the altitude at which a specific maneuver margin exists prior to buffet onset (minimum 0.2g for the FAA or 0.3g for the CAA/JAA operation). These margins provide 33° (FAA) or 40° (CAA/JAA) of bank angle protection to buffet."
(Reference the B737 FCTM dated October 31 2003, page 4.5)