Squid in dual stack ipv4 / ipv6 reaching out for services only served on ipv4 interface

Question

I am running a dual stack network and am running a server there (Squid, Apache, DHCP, Mail,...). The network is working properly. However not all services running on that server provide a listener on ipv6. Prominent example: miniDLNA.

Now as I have Squid running, all internal connections are also served via squid. Calling the miniDLNA WebPage is not possible that way. I was not able to configure Squid to fall back to ipv4 to reach a service not provided on ipv6 interface. It might not be possible. I use "proxy.pac" to solve this now by checking for that specific ports and return "DIRECT" in that case like that:

  if (
    dnsDomainIs(host, ".MYINTERNALDOMAIN.int") &&
    (shExpMatch(url, "*:8200/*") || // service 1
     shExpMatch(url, "*:4080/*"))   // service 2
   )
{
    return "DIRECT";
}

But I am asking myself, if there might be a kind of acl magic I could use that would manage squid to do that internally? And a good question would also be to check, if proxy.pac could be optimized. I for instance tried dnsResolve to be sure about the internal net - and that is a very slow approach.

Thanks for any ideas on that. Google was not helpfull in that case.