Hank is planing 10mm…? I really hope he reconsiders.
We can cut them smaller but can’t cut them bigger.
Here is my design attempt. A modified Nitro / PilotPTK design.
Its about 12mm, inner 10mm guide ring.
10mm ring is in the copper layer. Its not shown there but a soldermask would be over it. Most pcb fabs are more exact with the copper and soldermask layer, silkscreen can be off by too much for use as a 10mm guide.
Sinkpad went with silkscreen for their 10mm guide and it was clearly off.