Set the Duration or End TC of a Clip via AP

I've found that I can set clip Start Timecode with:

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clip.SetClipProperty("Start TC", "xx:yy:zz:aa")

However, this also pushes back the end TC by however much the start TC was changed, since the duration is unchanged. I've tried using the same syntax to try to edit the Duration or End TC of the clip:

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clip.SetClipProperty("Duration", "xx:yy:zz:aa")
clip.SetClipProperty("End TC", "xx:yy:zz:aa")

The API returns False for both of this, representing failure. Is there a way to set Clip End TC and/or Duration via the API?