Did you guys find the way to enlarge the GPS? I also new to X-plane and I thought same thing as you. I am trying to enlarge the GPS using the plane-maker. It is not perfect yet, but my 172sp has 150% big size GPS on 2D cockpit now. I haven't find the way to modify the background illumination image yet, it is still original size, and 3D cockpit was destroyed... probably it is possible to fix somehow. You'd better to make a copy file of 172SP for modification, if you try this.