When light levels are this low, motion blur (the blur of the subject moving during the exposure) and image shake (the shaking of your body during the exposure causing blur) are the biggest issues. Hovering around the 1/50 @ f1.2 ISO 3200 some images weren't sharp enough but those that slipped through the net I'm really happy with!
Their new production: The Last Fairytale
They are off to the Edinburgh festival today! Good luck guys!
To see more visit their brand new website: http://www.atlastheatre.info/
John