genkiller, so you're saying that there couldn't possably be a variable in score that you just might have overlooked?
im just throwing the idea out there.
I have a theory, i could be right or completely wrong so here it is.
after 4 ascends i played rainbow snails at lv 1. I got 97% acc, did not aim high and used no abilities. I got an S rank. My theory is that the lower level you are when you aim for an S more room for error is allowed making it easy to get an S rank.