With targets with a kill zone of 35mm to 45mm you can have up to 50% of the kill zone obscured (up to 6 in total).
There's nothing in the rules to say that they can't be obscured on the faceplate. Say for arguments sake you fastened a zig-zag cut plate over the kill. As long as 50% of the kill was visible is should be approved.
Run it past our organisers