That is a difficult question. Since all of the open panels must fit on the screen, changing one changes all of them. You can, with practice, arrange windows in such a way that all of the them will be the size you want (within reason).
If this does not suit you, you can always make each panel a window like in Premiere Pro 1.5 and then arrange them as you see fit. Use the Ctrl key as you drag a pane and it becomes a window.