Don't forget time between matches. Now if everyone is playing hopperball, less of an issue. But if pods are involved, either players are going to take time to retrieve their pods, or someone else will go and retrieve them. Plan on only 5 minutes per game, not 10. Honestly, it is 3 man, so what happens if 4 players get eliminated during the first 4 minutes, and they are noob teams? Everyone gets to simply stand around for 6 minutes while the new players are too concerned about making that mistake to lose the point, that it stalemates. So consider 5 minute games, one minute to collect pods, and maybe bet the next two teams out there to play, while the first two are reloading and such. There won't be a drag. Dedicate around 45 minutes per double match, meaning teams 1 and 2 are a match, 3 and 4 are a match, and give yourself enough time. Might not need it all, but then everyone can do some open play at the end, time permitting.
Think about this with the field ref. if the field supplies one ref, typical for your size, he is going to not only have to start and stop the games, but do any paint checks. All it takes is for a team to realize that the only set of eyes keeping them honest is involved in a 10 second paint check, and they may make the game winning move (Moving when they shouldn't, wiping, etc), and your league may be done before it really gets going. Having another team ref is okay, but really, what are they going to get out of it? Free entry or paint has to come out of someone's pocket, like yours or the field owners, unless you charge extra to cover this.