Vertical takeoff and landing (VTOL) vehicles are among the most versatile UAVs, appropriate for various missions. Given that there are still open challenges regarding the VTOL design, this paper presents the full development and test cycle of a tail-sitter. IMAV 2022 competition rules were used to define the mission. A multidisciplinary design and optimization strategy was defined with the goal of maximizing competition score considering design, manufacturing, and competition constraints. The resulting vehicle was designed to fly at 18 m/s while carrying 200 g of payload with a total weight of approximately 720 g. It flew for roughly 13 minutes at IMAV2022, helping its team to achieve 1st place at the "Package delivery challenge". Further flight tests revealed the ultimate endurance performance as 18 minutes.