After removing the existing pipes I had to drill out the drain valves to accept new pipework. I considered using copper, but as the pipes are so long with no way to anchor at the front end, I thought it would be too vulnerable to knocks and would require constant straightening. I settled on 0.7mm NS wire and having studied images of the set up of the pipes and the drawings in the Wild Swann profile, I repositioned the new pipework to be more prototypical. Here's the left hand set dry fit before trimming and painting.
And the left hand side after fitting and painting. I sprayed the pipes with red oxide primer off the model then fitted and brush painted the copper.
I thought the longer drain pipes would hinder the truck movement, but it's the steps which are the limiting factor to the side play on the curves.
Cheers,
Peter