If a University doesn't require subject tests and I did poorly should I send them?

<p>I wasn't really prepared for my subject tests and I'm not happy with my scores (680 math 1 660 lit), so when applying to colleges that don't require subject tests, am I better off just not sending my scores? Or do mediocre scores still look okay because it's something optional/extra? If which specific school it is matters, mainly UChicago, Stanford, and USC. Stanford recommends the subject tests but says not sending them isn't a disadvantage, and USC recommends them and says they can aid in consideration for merit based scholarships; but I'm torn between whether or not to send them. Any input is appreciated</p>