Invest in the 24" TruCut ruler and their ergonomic rotary cutter for your major strip cuts. The cutter rides on a lip and can't wobble around.
http://www.graceframe.com/site/rotarycutting Find a cutting buddy. DH and I do all our cutting together we double check measurements and each holds one end of the ruler. I keep my fingers on the far end of the ruler (out of the way) and he runs the cutter!