A programme which provides for graduated learning with continuity might run as follows:
CPL - 25 hrs Arrow lV followed by the Skill test (2 hours)
IR - 15 hrs Arrow lV
IR - 15 hrs Turbo Arrow lV
ME - 6 hrs PA34
IR - 18.5 hrs PA34
IR - 1.5 hrs 170A
ME - 1 hr Skill test
IR - 1.5 hrs Skill test
This way you start on a complex aircraft, and then graduate upwards in both speeds and complexity throughout the course.
Using the Turbo Arrow not only gets you into airways quickly, but gets you used to the Seneca approach speeds etc.
If you're up to speed on the Seneca, then do some time in the Sim towards the end of the IR module, never at the beginning.
Total time 11 weeks, plus 1 week safety / reserve time.
regards,
cfb