Main time is spent on removing the post's right sidebar -- looks like a vertical line. Hence, searching on keyword "width" throughout the xml file. Finally identify it a GIF picture from http://www.blogblog.com/rounders4/rails_main.gif , as the "width" is fixed inside a picture.
My solution is to comment it .
/* background:url("http://www.blogblog.com/rounders4/rails_main.gif") repeat-y $startSide; */
References:
http://www.bloggerguide.lk/2008/04/rounders-with-wider-post-area.html
How To Change The Width Of The Blogger Templates
http://blogger-and-money.blogspot.com/2007/06/how-to-change-width-of-blogger.html
Rounders 4 with a wider post area
http://www.bloggerguide.lk/2008/11/rounders-4-with-wider-post-area.html
Key Words: widen blogger.com template rounder4