The most important thing to consider when choosing or designing a carrying container is that no part of the model should be allowed to touch the container. A wingtip, even gently resting against the container wall, can be damaged by abrasion. I tried Foamcore trestles to support my models, but discovered that they left burnishing marks. I learned both lessons the hard way while driving some kits to a show. Even though I took pains to drive gently, I still had slight damage.
For aircraft, I found the best way is to use cut foam rubber and place the model upside down. I make cutouts for the fin, cockpit, etc, and leave clearance for any aerials and radio wires. The reason I like to have the plane upside down is that it is easier to keep an eye on the fragile landing gear. Foam rubber blocks are placed on top of the wings and fuselage to gently press down on the model when the lid is closed. That will keep the model from falling out of the foam padding.
The second most important advice is to make darn sure the container lid won't fall off unexpecedly! This is super important! Yeah I learned that the hard way too. If you have to fly with your model, make sure the TSA guys can either see through the container, or make sure that secure lid is easy to (intentionally) remove.
All that being said, the last time I flew with a model, I used a shoe box with an old belt as a container. I have a collection of cut pieces of foam rubber that I used to shim my models away from the walls and each other. I got lucky and didn't have any damage.