I'm just back from sim refresher in Europe on teh Q and for those who know the airplane, the INCR REF SPEED was on 95% of the time. That's our "safety" net giving an extra 20KTS margin to the SPS to account for potential icing. AFM says this button should go OFF when out of icing and when wings are clean (or look at the spigots on the windshield wipers).