Hi Noel, I purchased just one pack of these tail lamps recently with a view to establishing how they might be fitted to various pieces of rolling stock, so your success with them is interesting. In the absence of any information or suggestions on the IRM website (the support page, a note in the pack directs us to, does not exist), may I ask if you can be a bit more specific as to where you are locating the battery/control unit, I'm assuming that you are utilising the interiors of containers etc to the best extent possible? As regards the fertiliser wagons, while I have yet to attempt this, it seems to me they can be fitted with minimal surgery limited to removing a piece of the cross bracing inside one of the double stacked pallets, and simply pushing the battery/control unit inside and threading the wire and lamp through a small hole in the floor of the wagon beneath that pallet. The question Dave is asking about an unladen 42' bogie wagon was the first one that came to mind when I had these lamps in hand so I'd also be interested in your thoughts on that. thank you Tom