I am experimenting with cutting stencil sheets, too, using an SC2.
I was trying to cut these sheets:
https://www.hobbylobby.com/Crafts-Hobbies/Stencils-Craft-Paints/Stenciling/Stencil-Blanks---8"-x-10"/p/27039
And per advice from various YouTube videos, I bought a Circut Strong Grip (purple) cutting mat.
I am using a 60 degree blade, and have been experimenting. I've been able to easily cut the Test square/triangle if I run it a few times, but trying to repeat my fancier patterns doesn't line up and I get double lines, so that doesn't seem to be an option.
This stencil material seems very thick to me, which may be my problem. Even at max (500) pressure, it won't cut all the way through unless I do repeated attempts.
Measuring this material with my caliper shows it to be just under .4mm. This seems awfully thick, and I wonder how well this type of stencil even works with paints (even though the packing give instructions only mentioning using it for paint).
Any more tips to a newbie? I've had the SC2 for a few months and have used it to make various yard signs and even one jumbo sign (and a multi layer multi color logo), but this is my first attempt with trying to cut a stencil.