The IEEE 802.15.3 standard provides a framework for Medium Access Control (MAC) in high data-rate wireless personal area networks (WPAN) e.g. the mmWave piconets. The protocol also supports provisions for co-existence of multiple piconets in the form of Parent-Child hierarchies of Simultaneously Operated Piconets (SOP) operating in TDMA mode where each child piconet reserves a private channel time block (private-CTA) from the Parent piconet's CTA. However, due to the dynamic nature of the network, the private-CTA allocated at the time of child piconet formation is often disproportionate with respect to the actual load in the piconet. Therefore, a dynamic mechanism to adjust the private-CTA allocations among the child piconets is needed. In this paper, we propose some approaches for allocation of private-CTA among child piconets in order to enhance the utilization of total available channel time. Further, using a MATLAB based simulation environment, we evaluate the effectiveness of our approaches and validate our claims.