It doesn't stop it still looking a bit terrifying.

I can't see the original photos because apparently my work proxy doesn't like imgur today, but brush seals are the way to go with this. I used exactly this on the top of my garage door where the air gap along the top varies from between 9mm and 23mm. I replaced the stock adhesive strip with the strongest that I could find and scrubbed the mounting down before putting the strip up so that it wouldn't come off easily. Because of the great disparity in the gap size I also had to cut the brushes to an appropriate length so that when they closed, they didn't trap within the moving door and pull the brush mount off the top of the door-frame. The end result is I cut the brushes down to a couple of millimetres past the door that sits behind it when sealed. Thus far, no air leaks at all., which is saying something as the air that used to come in via that gap in winter would negate the heating in the whole third of the house, not just the garage..