Currently this can only be set when the lobby is created. It can't be adjusted between races without recreating the room each time. In private or public lobbies this would be of benefit. The solution would be to allow the maximum number of humans and AI to be adjusted between races.

I understand why the fields work the way they do was done so that space can be left in races for humans to join after practice or qualifying has started. However all I'd like is to be able to adjust the settings between races. This would allow a host to keep the grid size at the roughly the desired level as people join and leave a lobby.

I and other friends host fairly long private lobby sessions but for typically multiple 15-30 minute races for our club members. People join as and when they are available meaning numbers vary considerably.