A variety of vehicle-based and warehouse-based solutions are provided to increase the adaptability, utility, and efficiency of materials handling vehicles in the warehouse environment, such as a materials handling vehicle comprising a picking attachment is secured to a fork carriage assembly and comprising an X-Y-Z-Ψ positioner to engage and disengage a target tote such that movement of the picking attachment along a Z axis by the X-Y-Z-Ψ positioner is independent of movement of the fork carriage assembly along the vertical axis Z′ by the mast assembly and mast assembly control unit. The fork carriage assembly may comprise a mobile storage cart support platform defined by one or more cart lifting forks, and an anti-rock cart engagement mechanism configured to engage a mobile storage cart supported by the cart lifting forks.