In recent work by the authors [I. Noad and R. Porter, Renewable Energy, 114 (2017), pp. 1146--1159], the problem of absorption of ocean wave energy by a floating articulated raft was studied. Numerical computations were shown to be rapid under a wide range of configurations but became increasingly expensive in certain limits. These included rafts either wide or narrow with respect to the incident wave direction and rafts with many articulations. The current paper proposes approximations to each of these cases resulting in a significant reduction in the numerical effort required. Typical computations are more than 100 times faster in the case of the wide or narrow raft approximations, and it is shown that a simplified continuum model for an articulated raft predicts power absorption with less than a 1% error for rafts with three or more articulations.