I've tought of a "desperate" plan: If I am right, Shen Ling is producing a settler, right? Why not use this settler far away in the north, where GCA can't attack? Of course, the most safe place would have been the other land mass, but we don't have MM yet.
I know that we need the northern Iron, but I highly doubt that we'll connect it in time anyway.
Also, as GCA already has a map of us, do you realy think that they'll head for "unimportant" Cha Ching? If I was one of them, i'd go straight for Shen Ling, and we'd probably couldn't do anything about it.