Our gaming group runs between 4 and 8, with 6 being the common attendance.
We currently (In our RQ game) have a round robin of GM's running games set in the same setting, and each GM has a slightly different method of dealing with situations, but we range from the group facing a similar number (give or take one or two) of bad guys as PC's, or massive groups that are spread out through an encampment or some such.
Although we did have a situation where an army of 3,000 was effectively routed by one character lying in ambush and killing the enemy leader and then running like the devil for the city walls
Anyway, back to issue. . . I anticipate my Traveller game to run the same pattern, typically a like number of enemies, or about twice as many if there are 'mooks' with one leader type among them.