painting margins are used for the width so the graphics arent stretched...
i saw the new image... which one are you showing us? the one inside the frame thats cut down the middle or the outside one?
make sure you change the os caption height to the correct height of your frame top graphic (one image, not two put together for skinstudio)
as for the left and right border, their width is what you make it from your graphics... so its up to you, too wide of course is not recomended
if the image you are referring to is the one inside the window.. your painting margins have been pushed too far and are overlapping each other,
so its cutting the window off in the middle.