I'm really only going to echo the same sentiments as above, but...

If, you are choosing to group ride, it's imperative that everyone's on the same page. I'm not saying stay in line for 1000 miles, but at least follow some sound rules of thumb. Your lead and sweep riders need to be your two strongest and alert riders. If some in the "group" are going to not ride in a fashion that the majority is comfortable with, then you should split your group up into sub-groups or just not even bother. It just gets too sketchy.

I'm personally not a fan of group riding. I prefer to ride alone or with a couple of folks and call it good. There are times that I have chosen for whatever reason to group ride, but I definitely figure out quickly who's going to be the biggest risk factor and try to reasonably distance myself from them.

It doesn't need to be some dictatorial set of rules, that takes all the fun out of it. But, if you or others aren't comfortable, that takes the fun out of it, too.

Anybody remember taking their MSF class and the acronym "S.E.E."? Search, Evaluate, Execute. Well there's another definition and it works well with group riding. Is it "Safe, Efficient, Effective". I'd apply that to how your group riding is judged, then go from there.

Here's a link to an older, cheesy edit of an MSF group riding video. May or may not be helfpul, but thought I'd send it your way. Skip ahead to about the 2:50 mark.... that's where the group info. kicks in.

2 cents complete.

Good luck!