A buddy of mine w/ a svx powered syncro westy pointed  me to;

www.atvoutfitters.net/fuel_pack.htm

for a 27" x 14" x 2.5" rigid plastic fuel pack that fits flat in the westy
luggage carrier nicely, will support 800# on top of it, holds 3.28 gals, is
ventless, & you can stack them on top of each other for more fuel, etc. They
also have 'em for water. A little pricey at $71.96, but sits below the top
of the luggage rack for that no wind resistence, sleak, clean look we all
strive for?

FWIW,

Tom

> My extra gas is stored in 2.5 gallon plastic containers, one is OK for
> most trips, two for way off the beaten path. One Vanagon owner I met
> had a great setup which I am considering: he bought a plastic 6 gallon
> gas tank for an outboard boat motor and cut off the fitting that
> attaches to the motor. When you want to fill up the Vanagon tank, just
> uncoil the hose and stick it in the filler! No need to remove from
> roof.
>
> Keith O
> 84 Westy
> 90 Westy Syncro
>
> On Dec 5, 2005, at 9:01 AM, Automatic digest processor wrote:
>
>> Date:    Sun, 4 Dec 2005 22:01:10 -0700
>> From:    Bob Stevens <mtbiker62@HOTMAIL.COM>
>> Subject: Re: Transporting extra gasoline on/in a Westy Vanagon
>>
>> "So, I'm tyring to come up with a
>> safe and easy-to-implement solution."
>>
>> I carry the 5 gal. Wedco shown in Gary Lee's web pic link you posted,
>> in my
>> luggage rack, tied down.
>> Bob Stevens
>> '87 Westy Syncro
>> "Passion Fruit"