Yeah not a fan of diy funded. Keys and all...
That's it ..! I wouldn't trust any printing company with printing some private keys small enough to fit under a hologram. (And that would still be readable ever after...)
I'd trust casascius, and a few others, because they have proven themselves to be trustworthy and they have the setup to print these keys.
I wonder how to do that since I'd love to fund a few DIY crypto items myself. Just curious.
You should not just print out private keys on plain paper use QR codes instead.
This article describes the process using QR codes. I suggest you use adhesive
waterproof polymer printing paper for inkjet printers for the public and private QR codes. Attach the private key QR to the backside of the hologram and public key QR on top of the hologram if you wish. Avoids use of glue and the QR codes are printed on durable polymer paper