FPGA is a promising platform in designing a hardware accelerator due to its design flexibility and fast development cycle, despite the device's limited hardware resources. To address this, latest FPGAs have adopted a multi-die architecture providing abundant hardware resources with high yield and cost-benefit. However, the multi-die architecture causes critical timing issues when signal paths cross the die-to-die boundaries, adding another design challenge in using FPGA. We propose OpenMDS, an open-source shell generation framework for high-performance design on multi-die FPGAs. Based on the user's design requirements, it generates an optimized shell for the target FPGA via automated bus pipelining, customized floorplanning, and scalable clocking scheme.