Customized push-back pallet rack systems are indeed available, making an already custom-engineered system even more individualized to unique applications.  Push-back systems can be engineered to accommodate special pallets, such as extra-long and extra-wide pallets, as well as pallets that are not strong enough to support themselves.  In the latter situation, push-back carts are outfitted with additional reinforcement and wire mesh to create additional structure for support.