I agree with the no hole in the top or bottom 2 inches, but for the novice reading these posts, lets don't forget that the NEC requires derating when running 10 or more conductors together so basically what that means is that you don't need to drill to large of a hole because you can't run more than four 12-2 nm-b w/ground sheathed electrical cable cables together in a bundle without derating them and using a 15 amp breaker instead of a 20 amp breaker that 12-2 would normally allow. It is because of the heat generated by the 4 sheathed electrical cable cables together. (Five 12-2 sheathed electrical cable cables equal 10 conductors)
This is just for info only and not to get wrapped up in a structural discussion. I also assume Steve knows this already. Good luck.