I've read the something about having a txt. file in your spiral knights folder with the

-Dorg.lwjgl.opengl.Window.undecorated=true

But it seems that in doing this, it doesn't really change having it full screen for me. By this I mean that the only thing it did was unbind my cursor, since when I click out of SK it stutters the video on both my monitors like I was alt-tabbing from full screen.
Anyone know of a fix or something that might help? I'm running java 64 with an AMD processor that's been updated with it's newest drivers.