There's been some unspectacular, but nonetheless important, progress with my current Superbarn project.
The frames on these carriages are very obvious feature and I represent these by adding thin extensions onto the underside of the floor piece.
The extra thickness gives more support to the bodyside and makes the structure more robust as does the false roof I've made to support the top of the carriage which is the flimsiest bit of the body shell.
Normally I employ the false roof to mount the ribs which support the styrene roof skin but it's not strictly necessary on these carriages because we use a brass roof on them.
However it is still useful help keep the top edges square and straight and when glued in place it goes a long way to preventing any twist occurring.