I have custom cardboard boxes made for me. The larger guitar size types run to £15 each and they are only double corrugated. Packing can get expensive. Most people think such a box is going to cost £1 at the most! I used to hunt around trying to find suitable boxes but quickly discovered that I was spending far, far more time than what it was worth. I won't ship without a hard case and I also put in a couple of thin ply sheets to protect the large areas of the box. Add on the bubble wrap and it easily runs to £30, even without factoring in time. I've had one mishap with the shipping. Fortunately the damage was limited to just a tuning button. There's only so much you can do with the packaging though. If something weighing 25 Kilos happens to land on your box from a fair height the chances are it's going to inflict some damage.