After reaching countdown flyers should be respawned x seconds behind beacon. Where x is fence’s distance in seconds.
That should enforce the originally intended effect of the fence and keep the group together. Riders would not be eliminated from the group ride. If infront they would be put behind beacon and would have to catch up. Either you feel strong and don’t mind if you have to catch up or you’ll prefer to stay behind the fence. So it should help keep group together. That sould be of interest of any rider joining a group ride.