That said, here's a way to bypass some of those restrictions without editing the .bot file. First, check the "Rectangle" option. Then clear the grid. Then draw a new chassis. Then, move the "Height" and "Width" sliders. You'll be able to move the first four points you place anywhere you want.
Something else I've wondered: Is there a way to "collapse" points into one another when shaping the top panel? I ask because I want to be able to make wedge-shaped bots that go all the way up without that unattractive rectangular bit at the top.