Presentedness, construed as Humean force and vivacity, fails to explain degrees of temporal presence in the specious present

How does the property of presentedness work? How does one phenomenal characteristic manage to make one or more other phenomenal characteristics appear to be less than wholly present? The question is of interest because the only obvious way of construing ‘different degrees of presentedness’ is in terms of different degrees of Humean force and vivacity: a memory-image of a red balloon could easily be described as seeming ‘less present’ in this sense than a perceptual experience of a red balloon. B