I will vouch for setting up a Pirateship.com account. Saves you a ton of time at the post office and money on shipping. It's easy to set up, print out the shipping label and then just drop off at the post office. They will give you a receipt that you did if you want one. All the typical insurance and other services are available along with tracking. Search out some one that buys boxes by the bale and see if you can get the corrugated sheets that they wrap the boxes with when the strap the bundle together, then use that to wrap around the kit boxes . You can crease the folds with an old pizza cutter and make a nice neat wrap. If you want, take some scrap to make an end cap, but as Dennis mentions might not be necessary, and then tape securely. This really does a to make things tougher and really helps protect the kit. The rates today start off with the package girth, so it helps immensely to keep the dimensions as close to original as possible. Double boxing is nice but can add 50% or more to the rate. If it is REALLY nice collector box it may be worth it, but for a building kit, the corrugated wrap is worth the little bit of effort. I been selling off some of my stuff and have found that Lowes sells boxes pretty cheap and bought some of their larger moving boxes to cut up to make custom sized long and narrow boxes.
Use lots of tap along any seam where a flap closes. I have learned through the years that tape over any seam reduces the chance of a box edge hanging up on a sharp edge anywhere along a conveyor.
You nay get asked about shipping over seas. I have a package on the way to a guy in Canada that has been " in route to it's destination " since June 1st!! And the USPS tracking is useless. No one seems to know where it is. I have another in the ay to Australia. It is in the same situation, but finally cleared customs in Miami after sitting in Chicago for two weeks!! Lots of unexpected fees along the way and you also have to deal with the exchange rates. I may not ship outside the US again. Both buyers have been very patient, but getting an insurance claim against the USPS is very difficult from what I understand.
Type at you later,
Dan McEntee