I found the variable that controls the range of turns over which the AI will arrive, but is there any way to enforce a minimum value?

The original descriptions of Beyond Earth described the game starting off as a purely exploratory "you surviving on an alien world" game play, with other sponsors arriving many, many turns later. As it stands now, though, on standard I usually have another sponsor arriving within the first few turns.

I know I can just push the turn range up higher, but I'd rather have all the AIs arrive around the 30-40 turn range, rather than have them spread out from 0 to 80 or whatever.