An important aspect of any shunting puzzle is reliability when moving wagons back and forth over complex junctions. A key part of reducing the risk of derailment, is to add weight to the wagons. The collection of eight Hornby Rudd and Clam wagons have all been modified by adding liquid gravity lead weights to the chassis.
I used Liquid Gravity, poured evenly into the chassis, then fixed into place using Rocket Card Glue, both items are from the Deluxe range. Allow a full twenty four hours for the weight to dry in place, this added only two extra grams onto the total wagon weight but made a big difference in performance moving over junctions.