I had the same problem and was also worried about cooling. Plus, as I am tweaking my system, I got tired of dealing with the small'ish holes in back, having to pull the AVR out the front to connect things, then fiddle with the wires to thread the AVR back in place. My solution was to saw open the back so the back of the AVR was essentially open. I was careful to leave plenty of material on the back around and above the AVR (mine is on the bottom) so structural integrity was not significantly compromised (the back is essential to stability on a lot of entertainment units). I can easily see/reach all the connections in back, the AVR runs cooler, and the stand seems as stable as ever.
FWIWFM - Don
"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley