ooc: It's a cumulative +6 bonus, so on a 3rd attempt at a direction change it is indeed +12. Also, it's unclear to me what's supposed to happen to subjective gravity when the subject becomes unconcious or dead. It would be most convenient if the object simply stopped moving, but it would be odd for a dead character to be able to slow down more readilly than one making a concious effort to do so. I'm therefore inventing the following mechanic:
Unconcious/Inanimate object will maintain subjective gravity for 4 rounds. After 4 rounds, the objects absolute speed will drop by 30' per round until the object reaches a speed of 0 or lower, at which time it will come to a stop.
The primary alternative, that dead bad guys and unconcious allies fall away from you at the plane's top speed, with allies dying and treasure becoming unrecoverable, seems... undesirable.