MNT Tech:
If you are associated with FlightSafety in any way, contact the Toronto Learning Center and ask them to provide you with the code for the hot start malfunction from the Twin Otter simulator. Although it is for a PT6A-27 engine, it will be suitable for the -67. That code has been carefully optimized to provide a realistic hot start.
The most probable cause of a hot start is late ignition. Thus, if you are optimizing your code, light-up should be later than normal. Another probable cause is NG stabilizing at a much lower than normal value (e.g. 12% or similar), then the pilot introducing fuel.
My own belief is that the gas generator should continue to accelerate normally during the hot start.