4D-Flow MRI is a powerful technique for simultaneously imaging vascular anatomy and hemodynamics. However, its clinical utility is limited by long (10-20 minute) scan times. This work aims to shorten scan times by using fast RF pulses and convex optimized gradient waveforms. The waveforms are optimized with arbitrary shapes, and are designed to go as fast possible without causing peripheral nerve stimulation by including an additional PNS constraint. The optimized sequence is implemented and tested in flow phantoms and a volunteer. The data acquired with the optimized waveforms is up to 33% faster, with no significant difference in measured data compared to a reference sequence.