I trimmed my memory foam mattress topper with an electric carving knife. It did a great job in no time at all, with very little effort. Also, I followed the advise of a couple of other folks, here, and put the 3" mattress topper under the mattress. I then put a 1" corrugated foam rubber mattress topper on top of the mattress - like a pillow top mattress - and then the standard mattress protector. I want to tell you, this combination has turned out to be the most comfortable bed I've ever slept on! I'd recommend it to anyone!
2013 Eagle 266RKS
2011 Ford F-150 w/3.5L Ecoboost & H.D. Tow Package