Mach 4.7 Stability????

I am currently tweaking out a MiG-29A Fulcrum to go as fast as FS9 would "allow" I have swapped its AIR file with the one from JSF X-35B (It can handle the speed without losing control) I have reached a staggering mach 4.76 at 30000 feet
but the plane shakes violently but i can controll it. Is there a way to reduce the shaking so it flies smoothly??
