It's been over two years since I looked at it, but from memory I wanted a 8 KiB key pair that I could engrave. One was to be the public key that would be scannable, the other was the private key that would be kept in a safety deposit box.

The practical limit was 3KiB for the qr code and there was some metadata in the key I didn't want to lose. I can't remember if it was the private or public key that was giving me the most trouble. But the idea of just having something to point your phone at on a wall and read a signed message from me wasn't practical.