No experience with your application but ive used some of these sealant/adhesives.
Dicor 502-LSW -- great self-leveling adhesive sealant for rooftops. Designed for horizontal applications and great bonding strength. I used it to "glue" an alum. solar panel mount on my roof and it has held up to so heavy highway winds and washboard for a year now with no signs of separation.
Sikaflex 291 -- also adhesive/sealant. Polyurethane and messy but it holds great and I have used it as a vertical bonding sealer when mounting lights/racks/items to exterior of my camper
3M 4200 and 5200 -- great polyurethane adhesive/sealant. the 5200 is more permanent of a bond.
3M Proglaze at windows
DAP Dynaflex 230 -- never used it but gets good ratings as a sealant but also that it will mold up. Off my list for that reason alone.
DAP phenoseal NOT for horizontals or sanding h2o cuz it is water soluble vinyl adhesive.
these guys have good prices and alot of quality options.
http://www.defender.com - boating co's got this sealing stuff down.
hope this helps someone.