To be fair, it looks like session 1 and 2 had a number of groups of 3 in them and they both took 3 hours 30 mins to complete, session 3 only had pairs in it and it took 3 hours to complete.
So if the marshals had mucked about swapping odd shooters onto spare lanes etc, that would have delayed the start by another what, 10 mins?.. so there was a potential for saving 15-20 mins. In the grand scheme of things that's neither here not there really.
There was quite a difference between the earliest finishers for a session and the latest finishers - about an hour for session 2. Maybe an idea would be if once people finish or if there are spare bodies floating around they could volunteer to pick a lane to act as score keeper for the lane, that might help to speed things along a little and close the gap between the earliest and latest finishers.