I found this via deviant art, this really caught my attention because of the nice graphic representation of the Xi Gundam!
the article below is from GundamWikia
After completion of the RX-104FF Penelope, Anaheim Electronics secretly developed and built an improved variant, the RX-105 Ξ Gundam, and sold it to the terrorist group ofMafty Navilles Erin. The Ξ Gundam features a Minovsky Craft unit similar to the Penelope but integrates it into its main frame, resulting in a more sleek design and lighter mass. Unlike Penelope, the Ξ Gundam doesn't transform but deploys a Beam Barrier by flipping its chest armor up. The Beam Barrier is a device that creates a conical barrier in front of the Ξ Gundam as it flies through the air, making it more aerodynamic, and allowing it to achieve supersonic speeds in flight exceeding Mach 2. These minor changes give the Ξ Gundam an edge against Penelope in term of performance. Its armaments are similar to the Penelope but it has a larger shield without the built-in particle cannon that provided the Penelope better protection.