remember to put the start locations for the observer players.
AND REMEMBER to divide the active players and potential observers into different FORCES. TURN ON ALLY STATUS FOR OBS AND SHARED VISION FOR OBS. REMOVE VISION AND ALLY STATUS FOR PLAYERS. KEEP RANDOM COLOR ON.
BE SURE THAT THE PLAYERS ARE USER SELECTABLE and the observers must have a race selected by default.
when you start a map in scmdraft, you have an option with triggers(at the bottom)
select how many obs you want, you just have to change forces name, place start location and player settings(race, etc...)