For any new guys considering non-locking carabiners for your setup here is a video from our own
@Nutterbuster showing exactly why they are not considered good practice. See about the one minute mark for a visual example. You may say, "What are the odds of this really happening?" In reality, they are actually pretty good. Its a well known failure mode.
All it takes is a little slack in your lineman's between where you're holding it and where its attached to your saddle, a slight twist of the line and you lean back expecting the rope to take your weight and it pulls through. Next thing you know you're laying flat on your back wondering what the heck happened. Don't risk using a non-locker just to save a second or two.