Find this block of code IMG.userbannercenter in the css file for the plugin and replace with this IMG.userbannercenter { display: block; margin-left: auto; margin-right: auto; width: 100%; height: auto;}
Make sure you set the maximum size for the image in the dashboard. Add !important to the values width: 100%!important;height:auto!important; If it still does not work, I need a link to see it..