I think the thing to remember is that it is doubtful if you will see much or any reaction from the leaf springs when used on a plastic wagon with no load in it [whilst keeping the individual springs to a realistic thickness] but there is slack in the system - so all the wheels will be on the track + the individual springs still look so much better than castings and, of course, 'stand off' from the W irons - just like the real thing!
So there are other cosmetic reasons for using them apart from actual springing. Remember too though, that if you assemble them correctly [without getting any solder of any of the leaf sections!] then you are only asking ONE leaf per W iron to flex in response to the weight of the wagon, as the others below it just go along for the ride.
This also means that any of our W iron/leaf spring units as in the new kits will only require the same amount of pressure to respond whether they be 5, 6, 7 or 8 ply units.
And before you say all say anything - I know these new wagons are still not quite out + there are 19 new ones iminent - not 15 as on our web site!
Regards,
David Parkins,
Modern Motive Power