I have a 520 as the reverse light on the 11B, I have another that will be used on the BL. Just have to bend the bracket to install the switch and run the wires to the rear. The BLs stoplights are pretty bright since I used a relay in the circuit. The stoplight switch didn’t work, but I ground out the rivets holding it together, cleaned the contacts and put it together with small screws and nuts that I bought at a model train shop. I’d like to find a rubber cover for the SL switch, if such exists.