how to remove back plastic case from 1905?

I know this will void the warranty... that is fine. 

 

I could find 4 clearly visible screws inside the recessed area where the stand-plate

attaches.

I unscrewed them, and the plastic back case is still very firmly secured.

 

What else is needed to remove the back part of the case?

 

(I'm wanting to remove the back case, because I'm going to make a backboard of wood.. in order to attach a 2x3 grid of 1905.  I'm looking for the best way to attach the monitors to the wood.)  The majority of my work on the system is for the benefit of charities and helping organizations, so I appreciate any help that'll enable me to work more efficinetly : )

 

Jon