@Dpaux I was just reading a post in the Sims 4 forum that mentioned a max on lot of 20, but this information was posted in 2016, so it may or may not be accurate &/or current. It (Rosemow) also mentioned that, at least at that time, the Mod "MC Command Center" had settings that may help for this. I would provide a link to that thread but since it's old, and it includes links to Mods, it would not be appropriate to do so.
Hope this helps, as the thought of posing 27 Sims for a portrait begins to give me a migraine. Props to you for trying. I would love to see the portrait if you succeed!! 🙌
