I have a 4x4 2010 quad cab sport with the rough country 2.5" front level and 1.75" rear spacer with no issues at all.
Where did you hear that you can't go over an inch? The biggest concerns are that it wont be level (which is based of looks and an issue that you're trying to fix) and that it won't handle the same... but most of those concerns were expressed on much older threads when the coli rear suspension was still new and no one was willing to be a test pilot. I'm not mechanic but I can tell you that myself and other members are running 1.5" + spacers with no issues. If you would like to see some pis of my rig with the rear spacer here's a link to my thread. http://www.ramforumz.com/showthread.php?t=139401