Usually for those, most I've heard used were corset's with steel boning. It'll allow you to retain shape while giving you maximum stability.
RWBY: Blake Belladonna - Gambol Shroud FUNCTIONAL
Planned Cosplay 2017
- Everything all gold, woo!
Gilgamesh [Fate Series]
Kayle - The Judicator [League of Legends]
Sagitarrius Aiolis [Saint Seiya]
Genji [Overwatch - Ocre]
Geralt [Witcher 3 - Wolven]