I have not tried them myself, but some folks do like these:

http://www.rotopax.com/home.php

I have considered getting a set of these, and mounting them.  I'd like to hear from someone with experience with them.  Mr. Squirrel, how have they worked out?

mcneely

---- Roger Barkley <rvbarkley4347@GMAIL.COM> wrote:
> Am trying to come up with a way to carry some spare gas for an upcoming
> sojourn. Thought an outboard boat tank, (one of the flat ones), strapped to
> the roof cargo area might be a good container untill I purchased one,
> (Attwood). The thing swelled in the sun, made me a little nervous. What have
> others done, used ?  ('84 Westy).  Thanks

--
David McNeely