[389-users] Max number of users in a group?

We have a two machine 389DS multimaster cluster holding about 850.000 users. It's been working great for over three years now. But we are creating some big groups, that will have about 150.000 users in them. I've read in the list some posts about groups larger than that. But I would like to know if there is any limit or precaution when working with groups this size?