The leech can follow the leader all he wants before the startline, but he can not look inside the leaders cockpit. He thus can't see when or if he presses the event marker. If the leader wants to get rid of a leech, he can make a fake start without pushing the event marker. The leech follows, and is forced to push his event marker if he wants to start. The leader flies back, wait a couple of minutes, and then takes his real start. The leech either continues without the leader, or he flies back with the leader, but is now forced to wait 15 minutes for his next start, and can't start when the leader leaves.

Do this a few days in a row, and even a persistent leech will give up on even trying to follow. (At least if the theoretical concept works in practice).

I thus don't think it would increase congestion, on the contrary.

Pilots flying in team can communicate their thoughts on starting by talking in code. That's already pretty common in other aspects when discussing tactics on the radio. So, I don't think there is too much of an impact there.

I am not sure if another contest will try that first event marker system, but I like it as well. Would be good to compare if some did.