On the other hand, cutting a hole in the backplate makes it a hell of a lot easier to inspect the back of your board, to make sure everything's OK.
Or, if you're not running peltiers, you could put a small HSF there to take off what heat comes down through the pins or gets to the board by convection.
Or easy access to another temp probe for the really thorough among us... (or a place to stick your finger if for some reason you don't have another temp monitoring device

)
__________________
Everything aircooled

(I honestly don't know why you guys let me stay a member...

)
Always folding:
WXP Pro:
KD7R + Palomino 1800+
W2K3:
4x P3 Xeon 500 512KB (4 clients)
Linux boxes:
none

Had to put them to use doing *real* work.