I've used LUUMIA's Height Slider before... its cool to use for screenshots but as for gameplay it's not too fun since almost every animation gets messed up. Not saying its completely useless though since minor height adjustments won't completely screw up some animations.
I also noticed that it often bugs out the sims meshes and sometimes and their entire upper body will go invisible sometimes and you have to do or go somewhere to activate a load screen so all the meshes or reload for it to fix.
If you want to go extremely short, you'd use LUUMINA's height preset for your body, then also use LUUMIA's height slider and you can make your adult sim somewhere in between the height of a child and an adult. But i'd say they are a bit over half the height of a child, maybe 2 feet below the height of an unmodified adult, depending on the size of their head also. This is the height teenagers should have been set at instead of making them the exact size as young adults/adults and elders.
You can actually tell which sims in my screenshot that have the height slider, but also the preset enabled by the buggy display in their portrait... this happens because they are so short that the game doesn't know how to render their face in their portrait area.
This is a screenshot of the height slider I took when I was testing it a little while ago, I had some of these sims with the height slider as low as it could go. The the shortest ones you see there use the slider but also have the shortest body preset selected.
https://i.imgur.com/XojPQ5o.jpg