another way of making it portable and more stable with less drilling would be to mount wood notches on the top bars of the walls. You could then drill holes in a home made wood I-beam or clamp of some sort, allowing for more re-usabililty of the structure walls.
Maybe you'll find someone else to help you. Maybe black mesa... THAT WAS A JOKE, ha ha, fat chance.
My Buy/Sell 1337ness rating