There isn't space to have a scope attached to the rail so you'd have to take it off to put it away. Here's a picture just to show how it fits. Aside from that there's plenty of room for a couple of mags and somewhere for the optic to sit.
Would converting the selector to a non-ambi configuration improve the reliability of it? Mine's already so bad that I have to grab each side with a finger just to put it on safe