Hi Ian,
First, using the PC12 instead of the B1900D is OK as the latter is mentioned as "best choice" not mandatory aircraft. What matters is to remain within or close to the same aircraft class.
Then, the aircraft selection in tours is a known issue in FL3 but one that has an easy workaround:
- Select the aircraft FIRST (while the flight selection indicator is still blinking red)
- Select the flight (while the aircraft selection indicator is already steady green)
- Ignore the aircraft mismatch warning blinking near the tp of the screen
- Enjoy the flight, of course...
Andrei