Specify window height in lines

It would be useful to specify the desired window height in lines instead of a percent. When I plug in my external monitor, which has a much higher resolution, Guake takes up a huge amount of the screen (e.g. jumping from 25 to 50 lines) and I have to change it each time. (Thankfully I just learned about the Ctrl-Up/Down keyboard shortcut that makes this much easier.)