That harp probably has two little feet on it. Take them off for shipping!
We use UPS to ship harps all the time. The most important part is finding a box that is up to the task. It needs to be heavy weight cardboard and be big enough for the harp to be completely suspended inside the box, without touching the inside of the box anywhere. Try for a couple of inches of sturdy but flexible packing material all the way around the harp. Styrofoam packing peanuts and bubble wrap both work. We have, on occasion, sent an empty box to a harp owner for them to use, but of course that increases your shipping charges by another trip.
For insurance, the safest thing to do is to insure it for the replacement cost if you had to buy a new harp. The current price for an FH26 is $775, which includes a case.