I saw this setup at the Balloon Fiesta last year. They bought an extra set of base hinges and attached them to plates. The plates were then "nailed" into the ground. They used quick release pins to secure the arms to the trailer or the plates.
However: We had a windy day and I noticed something wrong with the awning. The rafter claw (cast piece at the end of the rafter arm) had broken and that side of the awning had tried to roll back in.
This is the only picture I have and it does not show the base. The piece that broke is where the rafter arm attached to the awning roll. This picture was taken before the break.
Wally Byam Airstream Club 7513