A new mesh created doesn't look good in the CAS

Hi. Please always provide files so that we would give an answer right away instead of guessing

It can be anything: the mesh is not vertex painted so it's not morphing, the uv_1 i s wrong so it's not morphing right, you transferred weights from the top instead of a full body outfit, etc

So, yeah, the mesh is not vertex painted, does not have a uv_1 map. You should put the patterns in the torso area, they fit. Avoid that bottom right corner because everyone puts everything there and you end up with CAS full of items that cannot be used together
Also, when you export from MD, there is no need to include internal shapes

How to transfer a uv_1 map:
- choose a reference that has as little sculpted details as possible;

- make sure both the reference and your mesh are visible and selectable;
- select your mesh, add a new map, name it uv_1;
- add Data transfer modifier, choose the reference as Source object, set the rest like in the pic, apply in Object mode.

Yes, you put them like this

If you plan on sharing you cc with other people, its best to keep that corner clear because people use accessories that are mapped there, so if someone will want to use your cc with eyelashes/jacket/bag/etc that is in the accessory category, most likely there will be texture overlapping
Also, forgot to mention, do not bake uvs with the body attached, it will take longer
Set margin to at least 5



Maxis swimsuits are texture based so it is not important whether it resembles yours or not, choose the most simple one. It does not matter whether it is a swimsuit or a lingerie set, they are the same