Thank you to everyone who has responded to my earlier questions (I hesitate to answer individually for fear of cluttering your mailboxes).
A family in our neighborhood whose children have outgrown FLL very kindly gave us their FLL table. It came with an additional L-shaped arm that you're supposed to nail in the middle of one of the sideboards and that would hang over the board to attach a shop light on. They said that this is because the lighting needs to be well-controlled in order not to confuse the robot's sensors.
This "light post" is not included in the current table design instructions on the FLL website. I'm wondering whether it's an artifact from the earlier generation of Mindstorms and is no longer needed?