Faking Sun Through Windows Interior

[Chance Severson]

Hey everyone, so I'm shooting a ballet short film that takes place entirely in a high school theater. The look the director and I want to go for though isn't a typical stage lit setup, we want to make it look as if there is light streaming in from windows stage left, but, of course, there aren't any windows there. My instinctual idea for lighting it was to get a 40 x 40 mirror board or two and just shoot the M18 I'll have available into it to create the most distance possible. In my head, this light wouldn't really need to be cut by flags to form a window shape, since it's bouncing off a square shaped board already. Has anyone tried creating a similar look (faking a window in a room)? If so, how did you approach it?

Also, is there a significant difference in shape between a CRLS board and just a matthews shiny board?

Attached are some previs lighting ideas I created as well as a picture of the location (everything will be happening on the stage)

Thanks!

Theater Pictures Link

 

[Vital Butinar]

I don't know if this applies but we recently shot a feature film and one scene took place in a living room where it was supposed to be morning. 

It's not the best picture but the gaffer put a streak of light on the back wall behind the actors. He used a spotlight and had an tele lens adapter on it where he could add some flags into the adapter. The light reminded me of those theater spotlights they used. 

What you're describing looks similar to me, maybe you could do something like that.