The latest IBA Proton Therapy system is a compact solution featuring a superconducting synchrocyclotron and a compact gantry. The compact gantry supports the state-of-the-art active scanning Pencil Beam Scanning technique. The gantry system can rotate around the patient to offer multiple beam incidence angles for tumor irradiation. With that method a small round beam is scanned over the tumor volume, allowing for an improved dose conformity compared to earlier techniques. This beam delivery method puts strong constraints on the beam properties. The goal of this study is to use simulation software (MAD-X and home-built Python libraries) to assess, challenge and improve the design of the gantry optics; to provide a high performance and robust solution.