I found it! I just needed to use the DPI offset setting.
Recent community posts
So when I realized that I can't use the mouse while Rustangelo is doing its thing, I was like, "That's cool, I'll just set up a second screen and watch something while it goes." Unfortunately, this seems to mess with the screen coordinates in a way that Rustangelo completely borks out and clicks in mostly the wrong spots, often those spots are on the other monitor. I'm just wondering if there's a solution to this in the setting somewhere that I missed or if you could possibly work it into a future release. So far I'm loving this app because I can put some really great signs into my RP server with it, I just wish I could do other things on my computer while it runs!