I tried putting the lighthouses in the positions on the diagram. Do they need to be in the door frame, or can they be on the outside hugging the wall near the door frame? If they need to be inside the door frame, I don't think that will work for me since I need to be able to close my doors.
Anyway, I tried a few test runs. I started with a full charge. The first time, I placed the dock in the bottom right corner of A2. It cleaned the entire A section completely, and the lighthouses successfully stopped it from going into B or C. However, it docked before crossing over and cleaning either B or C. I checked the lighthouses to make sure, and they were both set on lighthouse mode (on the minimum strength, should I try increasing this?).
Next, I reset the Roomba, and tried putting the dock in the bottom left corner of C3. Once again, the lighthouse stopped it from crossing over to A, but it docked before cleaning any other section.
After that, I tried taking the batteries out of the lighthouse to see how it would do without them. It became clear after a while, that it would do a semi-good job of the whole house, but not nearly as thorough as it would if it had the lighthouses. Today I'm going to try taking the battery out of the Roomba and lighthouses, put them back in, and try again.