Web Analytics IP override

Can I override user’s IP for web analytics?

I’m proxying analytics requests throw my nginx to bypass AD blockers and, as a result, I’ve got the same country for all users. In Google Analytics I can pass uip query parameter and put $remote_addr here.

Maybe web analytics can read X-Real-IP or other X-header to get IP from it? I tried X-Real-IP and X-Forwarded-For but it doesn’t work too.