Trust And Monster Mods.

I downloaded it, and it's correct I loaded it into texhammer and it shows the swimsuit textures.

The file sizes are:

Original file: 977kb

Modded file 964kb

If you're putting it in the original folder, make sure it's the proper install location for XI (rom/309/) that it's called 116.dat and turn off xipivot to make sure there isn't some issue there where it's loading another file.

Also make sure you're specifically calling Sylvie (UC)

If it's in the proper install location, then it has to be some problem with Xipivot having an old version of Sylvie or something else so unload that. on windower the text command is

//lua u xipivot

Also if you call her and she is wearing her normal gear, you have to zone cause it loads once and keeps it in memory for the next call until you zone.

I'm almost certain it's an xipivot issue.

You have a version of sylvie somewhere in your xipivot folder that is overwriting what you're doing