HAZARD RIGHT A
Extend your right arm at a 45 degree angle and point towards the hazard.
Looks to me like the HAZARD RIGHT A hand signal should stand for HAZARD RIGHT IN FRONT OF YOU.......HIT THE BRAKES.
I can't imagine that riding in a group, cruizing along, that you would want someone in front of you taking their hand off of the throttle. By God, without target fixation on the rider in front, you could come up on them pretty quick. Staggered or not, but I have never been a big fan of group rides.(at least large ones)
I too have used some hand signals along with vocal prompting over the years. The STOP AND PUT YOUR KICKSTAND DOWN signal seems to work too.