My edge pro has arrived and after some experimentation on a couple cheap Cryos I went to work on my XM18 Skinner. I sharpened it at 21 degrees. It seemed to take a while but it finally it feels like it's actually sharp. I've been carrying it ever day for a week or so now and I'm pretty happy with the performance. I'll probably sharpen my spanto xm18 at the same angle in the next couple days.
On the spanto, you might want to take that up a degree or two (because of the point on the spanto blade where the grind lines intersect).