Change handling of off-edge horizontal invariance checking.
Change handling of off-edge horizontal invariance checking.

andybarry/flight,andybarry/flight,peteflorence/flight,peteflorence/flight,andybarry/flight,andybarry/flight,andybarry/flight,peteflorence/flight,peteflorence/flight,andybarry/flight,peteflorence/flight,peteflorence/flight,andybarry/flight,peteflorence/flight,andybarry/flight,andybarry/flight,andybarry/flight,peteflorence/flight,peteflorence/flight,peteflorence/flight