not so good at the higher CASA approved MTOW increase
Reflects the local certification standard. The US stall speed based climb limit was replaced by the Oz OEI requirement .. more payload. Bit long ago now for the details to be fresh but, as I recall, Sleighs did the upgrade so it was probably Bob M or Rudy P doing the certification work.
Had many hours in the Shrike and loved every minute of it (.. ok, except for a couple of self-induced frights that shouldn't have happened).