Changing default tracking URL per site

I’m using wp-piwik & the PHP API to connect my Matomo install (https matomo dot a dot com) to two wordpress installs (https://c.example/ & https://f.example/)

Oh. two url per post limit. Fun.

I’d like to have these sites call matomo on their own subdomains - I’ve already set up config/config.ini.php so my clients won’t be confused about which sites to visit

trusted_hosts[] = "matomo.c.example"
trusted_hosts[] = "matomo.f.example"

I’ve already installed and activated ForceSSL, but there seems to be no way to change the base URL per site, i.e. wp-piwik always reports

Determined Piwik base URL is

is there any way to change this default per site?