Wingtip-mounted propellers have the ability to enhance the propeller-wing system performance. For inboard-up rotating tractor propellers, the swirl in the propeller slipstream can be used on the wing to reduce the influence of the wingtip vortex, decreasing drag. Furthermore, lift is enhanced by increasing dynamic pressure and angle of attack locally. In this thesis the performance of a propeller-wing system with wingtip-mounted tractor propellers is investigated using a low-order numerical model. The numerical model is used to investigate the influence of the main design parameters for wingtip-mounted propellers. Response surface analysis is used to predict the propeller performance throughout the design space, while minimizing the number of evaluations needed. This has led to insights in the influence of wing and propeller design on the performance of a propeller-wing system.