I remember very few cases where a GM was even needed, except for the (thankfully) few combats. Two seemed plenty. Also, I thought there was enough player-driven plot to keep us busy. Boss C's tiara, and various other power plays ... there was plenty of room to maneuver. (And a longer time slot? I'll pass! It felt like the longest night of my life as it was!)

The only reason I can see one would need more GMs is if you had a combat-heavy, RP-lite group, who started a bloodbath. In which case, the mod will be over soon enough. And as for more skills, my impression (based on my minimal involvement) is that most mini-LARPs are run on a "make it up as you go" basis. Seems fine to me.
I can think of things you *could* do -- put more details about the other PCs on people's sheets, for example -- but it would be too much to keep track of. You have these characters for four hours max, you don't want to spend the first hour digesting your character sheet.
Linda, aka Chief Babysitter
(And author of the "literally" deathless line: "You wanna maybe run this crown thing by the crime lab?")