You know, I have the mermaid mod but haven't played with them (Mainly because for a while there *not* having all of midge's supernaturals broke witch spells which was a mod I actually wanted to play with and editing the BCON for some reason didnt work and it was just easier to say whatever and throw them all in rather then figure that out. Supposedly this isn't a thing anymore but I've become resigned to having a dozen custom supernaturals now just to have them so I haven't checked)

...wait what was I saying?

Oh right! How do the custom tails work? I was under the impression they are tied to hair - is editing the swimsuit enough to change the mermaid's tail all around or will they randomly swap scales? I'm not sure if you use the full mermaid mod or just use custom content to simulate mermaids without the trait.