One other suggestion...

I've mounted some projects with the PCB on top. That way all you need is rectangulsr notches extending down from the top of the enclosure and these are fairly easy to do manually. I cut inside the vertical edges with a hacksaw blade, flex the section to be cut out with pliers until it breaks, then file the edges, starting with rough files then finer ones. It's tedious but works for short runs and prototypes. The only drawback is you see the edge of the PCB at the top of each opening and you may need to trim any long through-hole leads.