Go to your pull down menu and select "File/Document Setup". Change the numbers in the "Document Resolution" box to the size you want. I prefer 960x720 on an 1152x670 screen. This fully fills the frame and leaves room for the interface. As far as I know Bryce will always open the default 640x480 window size, just use "Document Setup", you don't need to "select new". In fact you can change the documant size (and shape) at any time while you are working on the image. I hope that clears up some of the confusion.