While partial reconfiguration on FPGAs has attracted significant research interest in recent years, designing systems that leverage it remains a specialist skill. Systems with a large number of reconfigurable modules can be challenging to design. Deciding on how many reconfigurable regions to use is not always straightforward, yet this choice impacts area efficiency and configuration latency. Current FPGA partial reconfiguration tool flows require the designer to have detailed knowledge of the physical architecture of the FPGA. It is the responsibility of the designer to decide on the location and size of regions. In this paper we introduce a formulation for determining the tradeoff between the number of reconfigurable regions, the allocation of modules to regions, and the reconfiguration overhead, represented by area and reconfiguration time. Throughout the investigation, we consider the heterogeneous nature of modern FPGAs as well as limitations imposed by current tools. We then show that adopting an optimal allocation can result in both area savings and a reduction in reconfiguration time over a standard approach to allocation.