Be forewarned that your choice of silicone is not a good one. NOTHING on an Airstream shouldl ever be siliconed, IMHO and from past experience. In almost every situation I have seen where silicone has been used, it has lead to sealant failure!
Older Aistreams used Vulkem and Parbond, newer units use SikaFlex 221 polyurethane and Acryl-R. Polyurethane sealant is a far superior product to any silicone and provides superior bomnding characteristics as well.
Search some of the threads relating to sealants on this site and you'll find that the general opinions of those here shy away from silicones.