I've taken the precaution of marking the strips for left and right. The strip for the right hand side has been snipped - not very clear in this photo - the top end of it can just be made out to the left of the 'R'. The photos are better quality than shown on screen - zoom in and you can see much more detail.

Note the strip that is attached to the left hand side - in the lower centre of the tender base. Normally, this strip simply makes contact with the boiler weight to conduct electricity to the loco chassis through the draw bar and that spring. We need to connect it to the balck wire of the chip - so it needs to be longer. I have already applied a thin smear of flux, applied solder to the iron and then applied a thin smear of solder. That is enough.