replacement LCD panel is slightly to big to fit into it

I have a mid-2011 model 27" iMac and the LCD panel needs replacing. I purchased a replacement refurbished 27" LCD panel from a supplier in China which has the correct LG part number label on it , LM270WQ1 (SD) (E3), however, when it arrived it had no mounting frame/bracket attached to it, and when I tried to fit the replacement LCD into my existing 27" LCD mounting frame/bracket the replacement LCD panel is slightly to big to fit into it!?

1. Does anyone know if the 27" LCD panels for the 2009, 2010, or 2011 model 27" iMacs changed size slightly?

2. Does anyone know it the 2009 or 2010 model 27" iMac LCD mounting frame/bracket fits into a mid-2011 model 27" iMac? By which I mean are all of the screw holes for mounting the LCD panel into the computer casing in the same location (alignment) with all 27" iMacs manufactured in 2009, 2010 and 2011 ?

3. Has anyone else had this problem and if so what did you do to overcome the problem? Currently I'm thinking that modifying the LCD frame I currently have may be necessary to resolve this problem, but I'd rather not commence doing frame modifications (potentially cutting the frame/bracket into 2 halves?) if anyone is aware of an easier solution?

Thanks!