Hello using the 'rapedotty' addon it is easy to get 1000 members, which is the cap.
the way you get more than 1000 members is by getting 999 members and when ever you want to invite other people, get a list of them first, and when you invite them, tell them not to accept the invite until the last second.
as long as you invite them before you have 1000 members they still are allows to accept it which exploits the cap