Ultrasound neurostimulation, a technique that modulates the brain's electrical activity, has emerged as a significant secondary treatment option for cases resistant to pharmacological interventions. The therapy is achievable through the application of a three-dimensional steerable ultrasound, directed by patient-specific stimulation plans. These plans are meticulously crafted through full-wave ultrasound propagation simulations. Nonetheless, the computational intensity required for calculating these plans poses a significant challenge, often reaching the memory capacities of contemporary graphics processing units (GPUs). By representing material properties and k-space operators more efficiently, we achieved up to 22% reduction in GPU memory usage, while accelerating calculations by 8.5% on an Nvidia Volta V100. This optimization introduced an error that reduced focal pressure by 0.5% without any focus movement, values that are clinically acceptable.