Okay done. Photos are attached. First two show the case for my Lady T, a steam tug of 37 inches long. The second two are the case for my Talacre, which is over 20 years old. The third two, are for my HMS Blandford, which is obviously an unfinished three masted 20 gunner from 1719. The first two cases were finished with varnish, but the third as it is purely for storage was left un finished.
All were cheap to produce, the latest one cosing a little over a tenner all in.
If you need to use the case to carry the model, ensure that it is made from a strong wood, thick enough to take its weight, when being carried. Also make sure you have a good solid carrying handle. The front and rear panels can be made of much thinner material, like ply as it is not load bearing. An internal frame is not necessary if you use a good strong wood.
If I can be of any more help.....Just ask.
Sorry about a couple of the photos, but they do give you an idea.