Take out the screw for the right hand side pickup and remove the pickup together with the two red insulating blocks. Separate the 3 parts and solder the free red lead to the top - take note of the cable routing. There is a handy hole there, but sometimes a wrap around the central column may be needed.

Reassemble the pickups and the red plastic blocks. Note that the lower red part has a short groove in the bottom. This corresponds to a short ridge in the chassis casting. Also the top part has a moulding which fits through the hole in the pickups, and a ridge which is positioned next to the tag with the soldered wire. Fit the pickups behind the two main drive wheels. This bit is fiddly. Dont force - it may take 2 or 3 attempts to get everything lined up. Screw it down. This one can be tightened reasonably tight to clamp the phosphor bronze sandwich and to stop the pickups from wobbling.