[Breakdown16]

Seems like not many people like to play doubles...(sadface).

But anyways, for doubles at least a certain amount of flexibility is required, since it's impossible to do many patterns while always using the same fingers for the same keys. Like for the P1 side (left hand), I usually use:
1 Pinky
2 Ring
3 Ring
4 Middle
5 Index
6 Index
7 Thumb

But this isn't always possible. For example, to hit 2345 simultaneously, I would use middle, ring, index, and thumb, respectively. Or for awkward pinky-ring trills like 131313, I might use index and ring instead.