Try editing your theme.inc.php file and set the width to 100% then edit IIP's configure file and set your left and right column's widths and then set the center to the difference of the other two and 100. That is, if your left and right columns add up to 40% then your center should be 60% and your "wide right" should be 80% (2 columns layout depending on page).
Hope that helps. Not sure what else to offer.
