If you edit the main skin's ini file (ex: SKINbedder\iGBB\iGBB.ini) the first line specify the starting width & height. If you embed Sb in a front-end that shouldn't even matter because the window will auto-resize.
Now the problem you are probably referring to is the graphics. If you need the bottom button bar to be 1024 wide instead of 800 wide, you will have to edit the graphic yourself. Then you will have to redo the INI file that has the co-ordinates of each button. There's no auto-stretch with Sb.
It's not hard though... I would start with a screen-shot of CF's button bar at 1024, then change the button pictures and map out the pixel coordinates.