I had a look at this today. The gasket material pulls right out, and reinstalls quite easily. I'm actually not sure what purpose it serves, aside from acting as a stop to keep you from opening the window too wide (I can see the square corners of the window hitting the curved corner of the track could cause damage).
So, I'd *guess* it's safe to do. I intend to send an email to Reace to see if he agrees.
I'm also wondering about the possibility of switching the rear window around, so that the opening panel is at the front of the window instead of the rear. That would put in under the awning. We got our mattress wet this past week when we left the window open and a shower came through. But, I suspect this would not be a good change. All of the sliding windows have the opening portion at the rear. I suspect that is necessary to prevent rain from getting in when driving.
2013 Escape 19 ("The Dog House") , 2018 Ford F150