EDNS and NAT

Hi list,
We would like to send EDNS subnets so the various CDNs can respond with local caches for our users behind CGNAT. They're on the standard 100.60.0.0/10 range so `ecs-add-for` shouldn't pick them up. 

Reading the docs, I am wondering if `ecs-scope-zero-address` is the right setting to be adjusting. I am setting it to a public IP in the nat pool, and I can see it being sent with tcpdump but it's sending as a /32. Is this is the expected behavior with the default ecs-ipv4-bits of 24?

We're using PowerDNS 5.2.6 recursor 

Cheers