I'm rebuilding a wall on my workshop. At the top of the exterior side, I have to fit something around the ends of the rafters above the J-channel at the top of the siding (there's no soffit.) That involves cutting 1-3/4" wide, 1-2" deep notches every 24". I have some fiber cement siding left over from another project that I wanted to use (mostly because it's free.) If I were using wood, I'd just use a jigsaw to cut the notches. I've seen circular saw blades and pneumatic shears for cutting the siding, but since this is a one-off project, I really don't want to have to buy anything expensive. How should I do this?