It's strange how opinions vary on this subject ,I have been riding motorcycles for 48 years (yes I know I must be tired lol) and ridden with large groups mostly with people I have ridden with before and in a group of eight or ten we usually travel single file with the pecking order sorted out pretty quickly fastest to slowest with pre determined stops along the way to allow for catch ups, the only time we ride 2 abreast is in town to reduce traffic light gaps and on the freeway to deter cars coming into our lane, I find it's better for overtaking slower vehicles in single file ,I have been on mass rides The Stone rides and black dog rides with riders each side at high speed and I must admit I don't feel comfortable not knowing the other riders skill level or experience ,maybe I am getting old!