Comccoy, from what I read it looks like you left out the white backing plate. I would worry about doing this at least on the front vents. These two don’t slant downward and if water is to run down to the bottom black portion of the opening it will enter the cabin. A sealed white deflector overhangs the black part and keeps the water behind the opening all around. Even if your rubber seal stops water when closed when open it most likely will enter whenever open driving or at rest. The thicker rubber seal along with the white deflector in your case should prevent this if it appears to be a problem.
Bill