[Plugin: Iframe] Want to adjust Iframe size

Hello I am using the 2011 WordPress theme and have customized it a bit via the stylesheet as well as adding a logo to it by editing the header.php file. On one page I want the iframe plugin to display a certain area of another website. There is a problem though. The iframe plug in seems to have a maximum width corresponding to the content area. I have tried some workaround that included adding a line to the functions.php in the theme but it was originally for image sizing (so that people could place bigger images in the contentarea) and did not work. Anyways what I need to happen is for the iframe to have a larger max width while keeping the contentarea of the page the same size. Where can I find the place that creates a “cap” on the max width of an iframe on my theme?

To add more detail the plug in I am using can be found here: http://wordpress.org/extend/plugins/iframe/