The wall cabinet itself is structurally sound for a 26″ span and will not have any issues. The main concern is screw strength into the wall studs when supporting a heavy load inside the cabinet. I recommend adding a solid wood cleat to the left wall near the face of the wall cabinet, and you can also secure it to the tall end panel on the right for additional support, as that panel will be anchored to the base cabinets below. Overall, this installation method is common and should not present any problems.