The nuts and bolts of those "mass arrivals" is that they shut down the airspace.. and all the planes in the group, who have all rallied, briefed and lined up at a nearby field (10-30 miles away) then do a closely spaced departure... and proceed at a specified altitude and airspeed.. so what looks like a "formation arrival" is pretty much a short hop with 30-60 second spacing between planes on a predetermined route.
in doing this special arrival, the arrival procedure that the NOTAM uses is shut down, and its much larger arrival capacity is suspended.
While it looks cool and sounds fun, Im gonna be "that guy" and say that the best, most efficient thing for the vast majority of everyone else is for EVERYONE not to not be a special case, fly the arrival as published and then all of you experimental RV types are gonna get all parked in Homebuilt camping together anyways..