The classical Kantorovich-Rubinstein duality theorem establishes a significant connection between Monge optimal transport and the maximization of a linear form on the set of 1-Lipschitz functions. This result has been widely used in various research areas, in particular, to expose the bridge between Monge transport theory and a class of optimal design problems. The aim of this paper is to present a similar theory when the linear form is maximized over real C^{1,1} functions whose Hessian is between minus and plus identity matrix. It turns out that this problem can be viewed as the dual of a specific optimal transport problem. The task is to find a minimal three-point plan with the fixed first two marginals, while the third one must be larger than the other two in the sense of convex order. The existence of optimal plans allows to express solutions of the underlying Beckmann problem as a combination of rank-one tensor measures supported by a graph. In the context of two-dimensional mechanics, this graph encodes the optimal configuration of a grillage that transfers a given load system.