Wheelchair tray tables offer a convenient way for wheelchair users to carry out daily tasks such as eating, reading, and using mobile devices. However, most tray tables are made to serve the majority of wheelchair users and are inaccessible to some with a limited range of motion. In our work, we address this issue by exploring the ergonomic problems and possible solutions. In this paper, we describe the human factors in the design and development of powered wheelchair tray tables. The process of humanistic co-design relies on the direct involvement of the targeted demographic in the design process. This ensures the outcome is centered around the specific needs of the individual. Our approach employs user research studies (e.g., interviews, questionnaires, and actively working with a wheelchair using co-designer) as a means towards gleaning valuable insight into the needs of wheelchair users. In these studies, we sought to explore their experiences with using tables made for wheelchairs. We also collected data about whether the tray tables required external assistance to stow and use, and the problems they faced using existing solutions. We then highlighted the various specific needs presented by the co-designers and questionnaire respondents. These needs are embodied into scenario-based personas in which they may find themselves in need of a table for use with their wheelchairs. Deriving these personas from our survey results provides an effective method of keeping the insight gathered present throughout the design process. Implications for design are discussed.