The USPSA rules allow for cardboard targets to be cut to reduce the amount of available scoring area (see 22.214.171.124), but let’s talk about a few things you need to keep in mind when doing this.
1.) Make sure enough A-zone remains. The minimum A-zone requirements are outlined at the end of Appendix B1 and apply to cut targets as well. For USPSA targets, at least 25% of the lower A-zone or entire upper A-zone needs to be available. For IPSC targets, at least 25% of the A-zone needs to be available. Also make sure that the original target and replacement targets are all cut to the same dimensions.
2.) Cut edge treatment. If you look at rule 126.96.36.199 it says that cut targets “must be fitted with a replacement non-scoring border, which must extend the full width of the cut scoring area”. So if you cut off the lower half of a target, you need to do something to that cut edge if that cut edge is exposed and not layered behind another target or no-shoot. You have two options. First you can add a strip of black tape (hardcover) on the cut edge. Second, you can replace the non-scoring border by adding a perforation 0.20 inches (0.5 cm) from the cut edge. There are tools you can buy to do this, but most people opt to just add a strip of hardcover because it is easier. And this rule applies to cut scoring targets and cut no-shoots.
3.) No holes in no-shoots. And just a reminder that 4.1.3 states that, “No-shoots may not have holes cut in them and be used as penalty targets that must be shot through to hit a scoring target.” If you want to use four no-shoots to create a hole to shoot through, go ahead. But cutting a hole in a no-shoot and requiring folks to shoot through that hole is not allowed. You can do that with hardcover, but not no-shoots.