@Black-Square So the turbine Duke's speeds (below) are much higher, I understand they are True Airspeeds, not indicated airspeed. But obviously I did not consider that. Ok, this is great education. The checklist values clearly would be variable as well based on density altitude I suppose.
Aircraft Performance (Turbine Duke)
Maximum Cruising Speed 320 ktas
Normal Cruising Speed 290 ktas
Economy Cruising Speed 225 ktas
Appreciate the feedback! Kirk