ORIGINAL: 3DAV8R

That is a very tall vertical fin on the Viper, I have mine with very little movement in a flight mode and a bit more in the landing configuration. When you start putting a lot of throw on that large of a fin you induce a large amount of side load (might be why people have had there fins depart there airplane). Just like on a full size jet, the rudder throw is greatly reduced at higher and higher speeds.