Determining course length for professional continuing education credits

Hello,

Majority of the e-learning we build has to do with professional continuing education hours.  The minimum amount of time that a course can be approved for is one hour.   The body approving the courses does not define what constitutes one hour of training, nor do they identify what steps they may take in the approval process.   

Since we are unable to see behind the curtain, I am hoping someone else has some shareable insight.  If you are in a similar situation, how do you determine the amount of time to request for accreditation? 

Right now, our best method is to build the entire course (interactions, animation, audio and all), than do sample testing.  It is not ideal, since we may end up being under one hour.  At that point a topic could get scrapped, or content that was already cut may need to be added back in to extend the time.

We have also been playing with the idea of using a word count to identify the approximate time.  130 words per minute is where we have landed, but it does not reflect so many of the variables that each course could have. 

Thanks in advance for the insights and assistance!