I'll start this with a disclaimer -- I don't "do" beats, which for me would be far too mechanistic. I write by instinct and let the story fall where it falls. For Kraxon, where I've had to produce an outline in advance for the series, I've concocted a story for each episode, but I've just gone for a beginning-middle-end approach, nothing more elaborate than that. When writing the story from the outline, this often resulted in three actual scenes, as I used scene breaks to increase pace and dispense with unnecessary filler, but it may well be there aren't in fact three beats per story -- there could be more or fewer, I've no idea -- as actual scenes don't necessarily correspond to beats, of course. (And incidentally, I've still spent hours taking a machete to the prose to make it fit the required word count...)
So it may well be I'm misinterpreting everything around the concept of beats. Therefore take what follows with a bucket-load of salt.
Anyhow, might it be an idea to start the other way around? What length of work do you think is sellable, and by how much are you overshooting at the moment? How long in word count does it take you to write each beat? Is the word count for each beat much the same within a story and from story to story?
If you want stories of only 5,000 words apiece, but you've calculated word count for each beat is roughly 1,000 words over each story, then there's your answer -- you have to restrict your stories to 5 beats.
If you find that there is no common word-length-per-beat, then that also gives an answer of sorts -- because the whole point of beats, I'd have thought, is pacing. So if the pacing is right, surely the beats should be cropping up at more or less the same word count. (Always allowing for the fact dialogue can be longer in word count than narrative, but can improve pace -- so you might need to look at narrative-heavy sections differently from those which are dialogue-heavy.) Can you affect this by borrowing my machete and tightening your prose, thereby bringing word count down?
If within stories there is a common length-per-beat, so pacing is fine for each individual story, but length-per-beat and pacing varies between stories, then that's a problem, as it means you can't extrapolate easily for new stories. Nonetheless, if you find this structure helpful, then it might be an idea to try and analyse further, to see if you can break down the stories in a way to reach a standard.
Otherwise, carry on experimenting. If you normally do eight beats, then for the next story try only four, and see if that gives you what you want in word count, making sure your beta readers don't feel shortchanged at the lack of story. But if any number of beats under eight leaves you unhappy, then it might be you're just not cut out to write shorts, and you should be looking at novellas.
Anyhow, good luck with it!
Unknowns are better sticking to the guidelines!
