Thanks, Charles.
I had a terrible experience with the local UPS store a few years ago and would never trust them to pack anything of value. They charged me almost $100 on top of UPS freight costs to pack a 50+ year old Gibson guitar in ATA case. The box was completely inadequate and arrived ripped in half. Only the ATA case prevented the loss of a $5k instrument..
I found all the appropriate boxes and corners through web searches, but they all sell in ginormous quantities and won't do onesy-twosies. Very frustrating.