Fixing a tunic in a shadow box display

[yum1829]

Hi all, I'm currently in the middle of a project at the moment. I'm making a shadow box display for my US 4th infantry Captains tunic. I'm making the whole thing from scratch which has been a challenge but is getting there. My question to people is, how do you or did you fix the tunic inside the shadow box to secure it so it doesn't move once finished. I'm not quite sure how to go about this and would like to know what people have used. Cheers, Daniel Kane