That's a good question. Not only spy drops, but actually would apply to any mission type. This was meant to be a 1 to 1 conversion of Bletchley's missions in order to preserve his mission ratios. I don't have the knowledge he has enough to alter those ratios while keeping everything historically correct. I guess if you want to give yourself some more variety, you can "modify" these ratios to retain your interest in playing or replayability. Sorry, it's not the answer you were looking for, but I don't feel confident enough in my limited knowldge of the ebb and flow of WW1 missions to make those kind of changes to this mod.
