Bobo, I have not had a issue with that and i have hit puddles at 40+ in it. There in my experience there has been very little water get in, it does allow for a little airflow inside aswell when you crack the windshield.
I have 3” gap between roof and window top, it lets in a lot of air.
I might cut a 1x4 just to play with up top. If it works decent I’ll use powder coated aluminum plate