This thread I started a few years back about the cutting of 1962 Topps Green Tints may be of interest to you...
http://www.net54baseball.com/showthread.php?t=226221
So many of those cards seemingly came out of the factory short side to side. And I've seen quite a few GT's in PSA slabs that were clearly not 2.5 inches wide, so there is definitely some leeway in the measurements.