This is a typical installation on an 07-17 Sprinter roof. There are two areas on the Sprinter roof sheet metal where the embossed ribs leave a flat area where a vent will fit nicely.Th photo to the right is an interior view of the vent. Note that the vent is located in one of the 2 sections that there is a break in the embossed roof ribs. In this case, we used silicone to seal up the installation.
Above, we have an installation where the vent is installed directly onto the embossed ribs in a section of the Sprinter's roof. We used plastic lumber (1/2" thick) to build a curb so our vent would be mounted to a flat surface. The plastic lumber is easy to shave and form to fit over the ribs. We then completely installed everything dry (no sealant) to get our fit-up right, then took everything apart after marking each piece's location. Next we cleaned everything with degreasing solvent. We then used black silicone sealant on the surface of the sheet metal, laid down the curbing, more black silicone on top of the curbing, then dropped the vent on and screwed everything together. We then cleaned all of the silicone (we used black silicone because it's contrast on the white vent frame helps with clean-up) and wiped everything with a little more solvent.