For my 1/2A fleet, I took a cardboard packing box, folded in the leaves of the top, and then put appropriate vertical notches down the two long sides. The notches are then protected by clear packing tape. A bit of thin foam sheet would be even better. Just point the nose down and slide the wing into the notches. One box holds 5 models safely, and you can poke a few smaller models (Mouse racers or logs) between the five if you accept a bit of likely hanger rash. You can also space them closer together if your landing gear can be unplugged. I did that on the Baby Skyray.
I've also seen carriers made of PVC pipe. Seems to work fine
Dave