My current research indicates that the more STR you pick up, the more DET is worth. I don't trust my own numbers that much because I don't have enough of them to tell whether it's my data that's flawed or that the underlying formula is more complicated than I'm hoping it is, but think of it more like DET ~= .46 STR at 664 STR, and DET ~= .43 STR at 634 STR.