Building a Blacklight Poster Frame?

[Black Sabbath]

So I recently got two blacklight posters and I want to frame them so I can do the blacklight effect on them. My idea is pretty much something along the lines of the other poster cases others have made here and hiding a blacklight at the top of the frame, behind the glass. I just need to figure out a good way to get the posters to stay in place (small magnets in the corners maybe?). Any advice or input is appreciated!