Do I understand that these will be pre-assembled fence panels, that you then just connect to each other and to the coop? Will there be corner (perhaps also line) posts sunk into the ground, or will the whole thing just sit *on* the ground? If there will not be corner posts (and, at those lengths, preferably a line post halfway down each side, too), then you need to either add them, or add horizontal diagonal bracing so that the thing cannot be pushed/fall sideways into a parallelogram shape and cause problems. Also, depending on what materials you are using, a 11 or 15' long fence panel can be rather structurally unstable unless there's a post halfway down. Really on the whole your best bet, in terms of structural stability and strength, is to suck it up and sink corner and halfway posts.
Also, maybe you are planning on it already, but I would strongly advocate adding an apron of wire mesh 2' or more wide, lying on or just under the surface of the ground along the outside of the run fence and strongly attached to the base of the run fence, to discourage anything digging in under the fence.
Good luck, have fun,
Pat