only advice is make sure you know all these 8 people really well. Strange social issue may arise with people that are not that familiar.
It is also important for everyone to understand that everyone has a hard trip, it doesn't matter if they've done them 2 times or 200times.
Only other thing is it would be wise to have someone that is not high, or is on a threshold dose to be a "master of ceremonies" of sorts. This person should have a little more experience then your average tripper. They should also not want to "control" the experience... ie they play music that the group needs to hear vs what they want to hear.
This person can also see someone having a hard time and take appropriate action. If he/she sees someone getting deep and having problems he can call a mental 'group hug' to help snap them out. What I mean, is you go around in a circle and everyone says something that they LOVE about that person (no negativity, stuff like "you have a great sense of humor" "you are a loyal friend I can call at any time" etc). If caught early enough this sort of thing can turn a weird trip around in a minute. Any and all bad trips are caused by doubt. All people should be open to talk about any doubt that comes into their mind.
"We're selling more than a cracker here," Krijak said. "We're selling the salty, unctuous illusion of happiness."