The fast spreading of new multimedia services and applications is pushing telco operator to identify candidate technologies for handling the increasing traffic load expected in the coming years. Along this line, satellite communications integrated with terrestrial systems is gaining momentum as a possible solution to overcome the aforementioned challanges. In this paper, we analize a multicast subgroup configuration problem for providing multimedia services over 5G satellite systems. In particular, an optimization problem is considered in order to maximize the aggregate data rate (ADR) with an execution time that is sensibly smaller compared to other solutions available in literature. Obtanied results, demonstrated as the proposed approach, hereafter named as Optimal Multicast Subgroup Configuration (OMSC), is able to overcome the limitation of sub-optimal subgrouping solutions by providing higher performance and, at the same time, low complexity operations.