No problem fiddling the electricity in this loco. Once side is uninsulated, so the chassis is live. The other needs some phosphor bronze (supplied) pickups.
These are fitted to a plate bolted underneath the frames. I filed the bolt head down a bit bit you're going to have to be no higher than track level to see it anyway. Using a bolt allows adjustment off the loco, although I just bent the wire with it in place. Where the pickups are close to the chassis at the back, superglue painted over the wire should avoid short circuits.
Now I have a sweetly running chassis. A bit more clean up and it's ready for paint. Where did I put my tin of brushable primer?