That may be hard to do as the receiver need to have an flow of air through it to keep it cooled off. If you block the exit may cause the receiver to overheat and fail. If you block the intake you will definitely cause the receiver to overheat and fail.
There is a chipset in there that gets REALLY HOT. If you tilt the dvr up, you may cook the PCB rather than the heat rising off the chip into the air circ.