Trouble with StructureMap and a public property I need to set

public interface IFileStorageService
{
    void SaveFile(string fileName, byte[] data);
}

public class TestFileStorageService : IFileStorageService
{ ... etc ...}

public class NetworkFileStorageService : IFileStorageService
{
    public string NetworkUnc { get; set; }
    public void SaveFile(...);
}

x.ForRequestedType<Func<string, IFileStorageService>>()
  .TheDefault.Is.ConstructedBy(
    () =>
    NetworkUnc  =>
    {
      var args = new StructureMap.Pipeline.ExplicitArguments();
      args.SetArg("NetworkUnc", NetworkUnc );
      return StructureMap.ObjectFactory.GetInstance<IFileStorageService>(args);
    });

StructureMap.ObjectFactory
  .GetInstance<Func<string, IFileStorageService>>()("something");

public class NetworkFileStorageServiceConfig
{
    public string NetworkUnc { get; set; }
}

x.ForRequestedType<NetworkFileStorageServiceConfig>().TheDefault.Is.IsThis(
  new NetworkFileStorageServiceConfig { NetworkUnc  = "something" });