In my 3912, I was able to squeeze my receiver between the TV and the bottom part of the area holding the TV. It is secured to the black felt cover in the entertainment area with velcro. Fits perfectly but it is a just a basic DirecTV receiver. My other receivers (with DVR) would not fit.
In the MBR, I mounted a flat screen on a mount with a swing out arm to the side of the area made to hold the TV. That left the major part of the TV box open to hold the other Directv receiver and DVD. This unit has an RF remote so line of site is not required.