BLI Paragon2 SD40-2 cab light

I really want to be able to turn the cab light iin this locomotive off or on at will. Before we go further, I found this thread: http://cs.trains.com/mrr/f/744/p/227822/2542728.aspx#2542728 , but while settting CV208 to 0 set the cab light off on power-up, once it is moving in the forward direction I cannot turn it off. The instruction manual says use F24, but that doesn’t do the trick.

Any other suggestions?