We operate UK certified AS 355N;'s and these had the AFM Group A supplements changed about two years ago to reflect the increase to 2600kg. Ours were already at the required mod state (torquemeters & limit light changed to indicate take off rating of two times 80% torque vice two times 78%). The 355N previously already had a 2600kg max AUM clearance, but for underslung loads. We use the 2600kg regulalry for clear area sites which gives us an additional 30 mins endurance.
NB did you notice that the previous Helipad graphs all started at 2540kg at ISA SL and the new ones now start at 2550kg at ISA SL? We can only use 2600kg for Helipad ops at -1000ft pa (quite rare in UK!). In most conditions above about +28 deg C (Also rare in UK) and/or above + 1000ft pa, the limiting factor is now the required second segment OEI rate of climb requirement (1.5%), not Helipad or Clear Area WAT.