How do I add custom parameters to TinyMCE Revo?

I’m trying to figure out how to add the the following custom property for my Revo 2.0.7 TinyMCE install

extended_valid_elements : "iframe[src|width|height|name|id|class|align|style|frameborder|border|allowtransparency]",

Methinks it will require a custom property, but I can’t really figure that out.

Is there a tutorial or other docs on how to do that somewhere?

Thanks