I'm not sure how to do this, but I also like it maximized and undecorated, for which I use devilspie. Devil's pie allows me to run a system command using the window ID. So my specific question is:
- What system command sets the transparency of a window using the window ID in Mint/Cinnamon?
But I'd settle for another good way to get transparency in urxvt in Cinnamon.