Matchmaker with strictly 1 VS 1 game

Hi all,

We're currently using Thunder for matchmaking in our WIP game. It is a strictly 1 VS 1 game which means that, as soon as a client has joined the host, the game begins and no further joins should be possible. So two questions:

1. With matchMaker.ListMatches(), is it possible to filter out games that are already in play? (Or simulate this function somehow, such as flagging a match as private as soon as the client has joined). Does it already do this if the maximum match size is two and two players are already in the match?
2. I'm assuming that "OnMatchJoined" will return success=false if the maximum match size is two and a third player attempts to join, is this correct? So that if a player attempts to join a game that has just been joined, we can cancel that attempt and refresh the list of rooms?

Thanks in advance,