Tex,
Since the topic of numbers came up, and since you mentioned score...
Simplest approach to getting a low score is to fill in as many categories as possible with the best numbers you can get. Most high scores happen because of empty slots -- which give you a very high number for that category -- since overall rank is determined by averaging all the category ranks on your score page. For example, if you were chasing a low rank you'd want to make sure that you captured at least one field from a C-47 and one from an M3/LVT; that you made some bomb runs, usually hitting a strat target with heavy bombs to get higher bomb hit% and points per death; attacked a city using PT rockets; destroyed buildings with a GV; and so on.
Getting a pretty good rank just requires paying a lot of attention to the quirky details of the game scoring system, filling in those blanks, and being careful to not "waste" sorties with statistically harmful behavior (like taking off from a vulched field, or flying bombers and dying, etc.). Getting the very best ranks requires that kind of gamesmanship, plus the skills to get lots of kills fast, etc.