Wing extensions and winglets have the potential to reduce the induced drag on tiltrotor wings, as they operate at relatively high lift coeffcients. To investigate this potential, the aerodynamics of the wing-proprotor system were explored for two cases - a planar wing and a wing with a winglet. For each case, a theoretical ideal loading condition was identified both with and without proprotor effects. The ideal loading condition was achieved through twisting the wing, and the resulting performance characteristics were evaluated using a recently modified, higher order, vortex-lattice code. Proprotor effects significantly altered both ideal loading conditions, and the twist distributions required to achieve them. The performance of the designs were then compared under different modeling assumptions within the analysis code. The span effciencies of the ideally twisted designs were significantly higher when single-sided interaction was assumed, as compared to full interaction. Modeling with wake relaxation had very little effect on lift distributions, but had an effect on span effciencies, specifically in the winglet case. The investigation provided valuable insights into the aerodynamic complexities of designing wing extensions and winglets for tiltrotors.