Our FC almost had the same problem, but we found a solution. We had 10 people and wanted everyone to be able to do Coil so I split the groups into 2. 6 people goes in the 1st group and the 3 others goes in my group. We then recruited people to fill the spots and eventually ended up with 2 static groups. My group waits for the 1st group to do their coil run to see how far they get. If they get turns 1-3 done, my group completes turns 1-3 then we merge the strongest players from both groups for turns 4-5. If I end up recruiting more people to the FC, i'll help the new people form their own static and do the same. I might split up my group for the first 2 weeks just so we can help the new group progress.