Four-arm four-flipper disaster response robot called OCTOPUS, which has 26 degrees of freedom (DOF), has been developed to engage in complex disaster response work. OCTOPUS adopts a multi-operator single-robot (MOSR) control system, and two operators manually control the robot. The pattern of control-authority allocation (CAA) for two operators largely affects performance of MOSR systems, so this study conducts usability tests in various CAAs, and derives a reasonable CAA pattern. So far, there are no uniform standard allocation rules for flippers and crawlers in multi-limb robots like OCTOPUS, therefore we specify five CAA patterns for investigation. Three fundamental tasks that whole body of the robot must be cooperatively controlled were conducted to test the usability in each CAA pattern. From the results of analysis, we found that pattern 1, which one operator controls front two arms, flippers, and crawlers, and another operator controls remaining back parts, had best scores for all tasks, as well as pattern 2 had the best distribution of workload between two operators.