hey Joseph,
you may wish to check out the viewer methods available in the javascript api. that should give you an idea of what else is available in the cr 2013 viewer.
http://help.sap.com/businessobject/product_guides/sbo41/en/sbo41_cr_js_api_en.pdf
weblayout only shifts the viewer into the top left corner so as to eliminate the gray space created by a screen size larger than the report page size.
most of the properties available in the js api are also available as url switches for opendocument. some of these properties are also used in the webelements library.
also, the cr2008 viewer had more properties available it seemed to clean up the viewer so that it could be embedded seamlessly into web pages. cr2013 seems to be missing some things.
-jamie