[MT nester]

Home Depot has a 3M product I cannot recall what it is called but it is a urethane seam sealer for marine applications. Really good **** availiable in tan or black.
Also look in the yellow pages under "auto body shop, supplys"
Those places have lots of good stuff for cobra builders.
There are several mfgrs of seam sealer/adhesives that will do the job (3M, Lord fusor, Kent) but most are a two part system that must use a mixer/applicater gun that is kinda' expersive.