The 9 degree wedge on e-bay is not long enough - you need the 25" one. I originally purchased the 14" one (LQS actually ordered the wrong ones for class). I asked the instructor if we could at least use the shorter one to get the angle, then use a regular acrylic ruler to extend the angle. Unfortunately, the cutting is really the trickiest part by far, and I'm glad she said she didn't think it would work well.
I ended up keeping the smaller ruler for final cuts, and ordered the longer one for initial cuts.
You make 25 cuts from 2 strata sets, ranging from 21 3/4" to 3 3/4" (remember to take that 3" off as the ruler is not really 25" long).
When cutting from the first and second strata, DO NOT cut from end to end. At the narrow end of the wedge, go across the end of the wedge. The scrap fabric must be kept intact so that you can make the final cuts from those remainders.
Attached are pics from my top (before trimming to a smooth edge, sandwiching & quilting).