On Thu, 22 Jul 2010 13:04:13 -0700, Steve B wrote:
There are lots and lots of variables here. But the one constant is that gas
is very flammable, and extremely easy to ignite by several normal every day
methods, including static electricity from a poofy sweater.

I think we've answered one of the questions:
Is it all that dangerous to keep 20 gallons of gas in the back yard?

We all know that there are plenty of dangerous things we keep around our
house (I have 1,000 gallons of propane in a tank ten feet away from the
house, for example), and gasoline in portable storage containers is one of
those things nearly every one of us has in our garage or shed.

As far as I've read in this thread, the only limits I have in storage
(besides common sense) are the ones from OSHA which I'm well within.

But I don't think we have been able to answer the second question:
Is it illegal to trasnsport more than 5 gallons (California) in a car?

I'm searching the California codes as we speak and can't find anything
telling me how many 5-gallon gas jugs we can carry in the trunk of a car:
http://law.justia.com/california/codes/veh.html