With that new saw you will still have problems with power. If you can hit low RPMs you might try a butterfly cutter to make a smooth jig, and the router your actual pieces.
If you don't have a router, try one of these
Not bad for 30 bucks, just keep the RPM low, or you will have a really memorable moment.
One of these is an option. You can get one that chucks into a drill and is infinitely adjustable. I've used one to cut a hole in a sheet metal side panel, makes a nice clean cut. They can be a bit dangerous to use if you are inexperienced or have a poor clamping setup. The tool likes to grab if you cut too fast.