[ATTACH=CONFIG]604344[/ATTACH]This is my machine which I bought used off Craigslist about 10 years ago. It is a hand crank and not the electric one that makes a lot of sense now that I am older. This is the 5 strip 1 1/2 inch, an older model as the newer ones have a different color foam inbetween the knives so you can see where you are going. I have cut 6 layers, but that is tough going and I would stick with 2 or 4.
The whole premise is that you need to have a fabric that is Goldilocks: Not too big, not too small.
It needs to be wider than the last knife. This die is 7 1/2 inches wide, so my fabric must cover the outside of both outside knives. Now of course you will waste some, but I seem to waste a lot more using my rotary cutter. I am forever cutting it wonky.