You may change the connections by changing the default.cfg file of the script.
Open the default.cfg under the script, and change the value of MaxConnections under WEB, like below.
[WEB]
MaxConnections=6
As I know, the API web_set_connections_limit should still works. It should be a doc issue that missing help of the API.
You may try to put this function to your script.
web_set_connections_limit("10");