Chart width

Hi, great plugin but I have a problem, I have created a line chart displayed within a div of around 1100px, without a the chart_height attribute set the chart will nearly fill the div width but not completely, the height is far too squashed to be any use so I set the height which then shrinks the chart meaning it is nowhere near filling the div width, it seems to centred it as well, I suspect that the chart will only ‘fill’ the div with a height set to zero. How can I make the chart full width and set height without it affecting the width?