For the record, I understand the OP is looking for something temporary for use as a one time shipping container. However, for anyone reading this and considering the import cases as a permanent solution, here's my take.
I have two different import cases and they fit the perimeter of my 4-digits well enough, but the neck angle should be compensated for by angled padding beneath the body which the import cases don't have. The lack of padding means any support stops about five inches above the heel and doesn't start again until the bottom 1/3 of the body. Combine this with any downward pressure from/on the top and this has heel break written all over it.
Here's a handy illustration:
Support stops<------5"------>neck joint<-------approx 10"------->Support starts
You could (should) add something to this area to help, but IMO it's still a bigger risk than necessary. I don't know how different (if at all) the neck angle is between "vintage" and modern Standards, but unless it's vastly different this problem should exist for both.
I'm sure someone here can dig up the TKL model number used by New Hartford. Why bother with something that doesn't fit perfectly when there are cases that do?