Not familiar with that model either, but davenn's probably right about missing a screw or more.
I've found some screws in other models under footpads on the bottom of the chassis, and in other 'hidden' places.
Good luck finding it easily.
I do remember seeing a couple of Sony chassis, where you unscrewed the cover, and then slid it back to
lift if off the chassis, but you should have the correct answer with davenn's manual to you.