im most cases, you will need to flip the polarity. when im micing the bottom of the snare, its never angled, i have a c414 flat against the snare (obviosuly not right against it, but the angle is straight).
the top mic varies, depending on the snare, the song, and the drum sound. but you will usually need to flip the bottom. yes, listen and see, but more times than not, you will end up flipping.
but it's soo important to mic the bottom. on mixdown you have much more flexibility.and considering that a vital part of the snare sound is made from the bottom, its a good idea to mic it.