If it's useful, this is how Glasgow Green CC organise the club runs.
Basically, 4 groups of varying pace, all riding the same route with only the slowest group having a no-drop policy.
It IS very prescriptive and maybe too much so for some but it does work pretty well.
From the website:
"We will split into STEADY, CHALLENGE, CHEEKY CHALLENGE and RACE PACE at defined and agreed points along the route, and we will aim to minimize the stops.
Groups should contain between 8 and 10 riders.
Steady is steady and usually sit between 14 – 16 mph average.
Challenge should push your ability and sits about 16 - 18 mph average.
Cheeky Challenge is slightly faster and is around 18 - 20 mph.
Race Pace should be regularly and consistently over 20+mph
**these are the averages you should expect over the course of the ride in the above groups and there will be sections ridden faster and some slower depending on road profile and conditions
**Please remember to communicate within your group. If you get split due to junctions, traffic, roundabouts then get back together. If you get split as someone is dropping off the pace then that rider steps down a group, (or steps up if going through to hard)
**If you need to ask the group to slow up, we would suggest you step down as you may be in the wrong group
Please pick your group carefully and remember that all groups work together to promote group riding but steady is the only group that rides at the pace of the slowest rider and the other groups don't wait for dropped riders unless agreed amongst the group and riders on the night"*