Well, for my two creds, I have run games in various systems for up to 20 people, and getting to 8 is about the limit of reasonable time and attention for everyone. I have most recently run a table for 7 players in SR, and it went fairly well, as we had a TM, a decker, (aka the decker team), a face, a mage, a rigger, a sammie and a weapon specialist. Everyone had their special niche, and we had enough overlap skillwise that most things were covered when someone could not show up. Would have been nice to have a second mage, but that would push me as GM to the edge of reasonable playability. Everyone had fun, so it was a success, but it was definitely at the edge of playability. So my advice is to first check with the existing players, and then if they want to add players, look at the existing characters and suggest to any new players that they consider creating characters who fill gaps in the roster of roles. And be aware that running 6 or more players is hard work. Good luck.