@doutoku : I think I found the difference between a hairstyle built into a costume and a normal hairstyle and also why it's possible to perfectly import a hairstyle built into a costume to another costume.
MOT01_Head is the parent bone of WGT_Hair in costumes including hairstyles. When you change it to ---------- and delete MOT01_Head, glitches happen ( ---------- is the parent bone of WGT_Hair for normal hairstyles).
Parent Bone reassignment may be the main problem when it comes to importing hair with TMC Object Tool.

Sorry for posting in English.