This paper describes a laboratory experiment design that has been developed to assess a new political economy institution for possible use in trade negotiations. The objective of this paper is to explain the implementation of this experimental design in the context of a horizontal model of a political economy. This environment is much more complex, and in a sense more realistic than the simpler environments considered in our [1990] companion paper. In Section 2 we briefly describe a general Multilateral Bargaining institution once again, so as to make the present discussion self-contained. In Section 3 we describe the present focus on a horizontal model. In Section 4 we run through in some detail the numerical solution to the parameterized version of that model. Finally, in Section 5 we detail the use of computer software that has been developed to implement the laboratory experiments with the Multilateral Bargaining institution proposed here