Keeping in mind I'm not operating in any official capacity, here is how I believe the qualifier works.

Four blocks of seven - full double round robin
Top one in each block go direct into main event.

Next two in each block go into a new block of eight - unsure if this is single or double round robin.
Top four of this block go through to the main event.

The next two go into a playoff with the two highest placed, available under 21s that have not already earned a place in the main event.