End boards out of hardboard for transport and a bit of weight in the SSA scrap wagons.
These are Cambrian kits and although there is weight under the middle, occasionally the ramps flip the ends up. So some slices of lead sheet (next door haven't spotted the leak in their conservatory yet) at either end in all three vehicles. And some foam to stop them rolling away.
These have the same problem as the US boxcars that I used on Einsford Mill, that being that they run too well - there's not enough dead weight. Result: loco draws up to couple and just cannons the wagons up to the buffers. So a little foam PVA'd under one axle of the rake brakes them just enough to stop this.