I understood it was flown at the Burbank airport. I believe they were
stored across the street. (That's the only area that matches the
description of 'mock-up'.) Back then, the whole area was under the
camouflage that covered most of the plants during WWII and it wasn't
uncommon to see traffic stopped whilst a P-38 was towed across the
road for one thing or another. As for skunk works. As projects go,
this one was a couple of guys working in shed at one of the shops
where they Lockheed cranked out 'shapes,' stringers and the like. It
was NOT an aircraft assembly plant but a 'plant' that made parts for
the other plants. There were several buildings there, as I recall,
some of which used to be assembly plants but were turned into office
and shop space as the war progressed. I seem to remember long lines
of people... maybe it was a cafeteria or something like that :-)

-Bob