facebook social plugin - not able to specify size

I'm running into this simple issue but not able to find any docs for this. I was using the following facebook login button which was displaying a long/large facebook login button and this works perfectly fine

<fb:login-button length="long" size="large" perms="publish_stream,offline_access,email,user_events,rsvp_event,user_about_me,user_location,user_website,sms"></fb:login-button>

Now I wanted to use the social plugin and show the faces - so I saw the sample code here - http://developer开发者_JS百科s.facebook.com/docs/reference/plugins/login

<fb:login-button show-faces="true">

But I'm not able to specify the attributes length and size here - even if I do add - the size does not change

<fb:login-button show-faces="true" length="long" size="large"></fb:login-button>

Any ideas on how to increase the size of the button.

Thanks

You cannot change the size of the button when using show-faces="true" at this time.