I would like to have a part of a garment (for example, the sleeves of a jacket) to use syflex..

So I do the following:

The jacket is enveloped with a whole rig for animation, including the sleeves.

I extracted and keep the sleeves polys and work as a Deformer Cage and use it later.

Also, the original jacket, I selected the sleeve areas by vertices to form a cluster, to define the deformed area that affected by the deformer cage.

Syflex simulation of the extracted sleeve polys.

After the simulation, I selected the sleeves cluster and deformed by cage by the extracted sleeve polys..... but the result isn’t I expected.....

I don’t know what’s wrong and is there any work around?  Thanks.

Extract the polygons you want to simulate, add syflex to them, pin the points wich should stick to the rest of the jacket to it. Simulate it, bake it, merge the extracted part with the jacket again.
There you go finished :)