Just a quick update. After several attempts, breakages, etc... the front vents are now installed. I did not glue them permanently in place as they are such a tight fit that friction itself is enough to hold them in the vent surrounds. The vent surrounds are tight enough fit in the skins that they too are not able to slide in or out. For the moment, I'm going to leave things alone, until I find a good reason to secure them further.