Mick,
I am not a player. I just set up these balls to picture the phrase that comes from the game of eight ball - "behind the eight ball". As I recall a rule that I used to play, I cannot hit the eight ball first. So like you, I would play a shot off the rail, knock the 7 out of there, and try to get it next time.
Without knowing your rules... If I was on the red 7, I'd play a sneaky off the left cushion shot to land slowly behind the 7 to snooker you from the black. How do you play that shot?