Finally got round to doing some more work on the (first) turnout this afternoon. All that remains now is to install the wing rails, tiebars and operating mechanism, add cosmetic rail breaks and fishplates, and wire everything up.
My solitary P4 wagon glides through the turnout without the slightest bump or lurch, even without wing rails, so that's a good sign!
Each rail has two copper wires soldered to the underside which pass through holes in the timbers and baseboard. The soldered joints are concealed with cosmetic chairs making them completely invisible.