Hello,
--target-hosts can also reference a json file, see the docs here and you can maintain this easily. For just one cluster you only need to specify the "default" key e.g.:
{
"default": ["127.0.0.1:39201"]
}
There should be no problem with limits to the array.
re: testing behind a load balancer: as @Christian_Dahlqvist said, are you sure your load balancer works correctly? This discuss topic may also be useful to read.
Dimitris