How to start a 4v4 “Squad Rush” style match in Portal and set minimum players?

Hey everyone,
 I’m trying to create a small 4v4 (8 player total) “Squad Rush” type experience in Battlefield Portal.
The problem is that the match won’t start unless there are 16 players, and I can’t find any setting in the Portal Builder to lower the minimum players to start value.

Is there any way to reduce the required player count — for example, make the match start with 2, 4, or 8 players total?
If that option exists, could someone tell me exactly where to find it in the Portal editor (Game Mode Settings, Rules, or elsewhere)?

Thanks in advance!