Ahh… sheer fabric… yeah thats a difficult one.
You can use masked with dithered opacity, you may find the result is smeared when moving the camera though.
Another option you could try is to brute force it using sorted translucency. In the actor settings there should be a sort triangles option:
You can try enabling that on your mesh with the translucent material. It may be unreliable though, and sorting is per-triangle so you may still get some overlap