Bearing surface really has nothing to do with being able to stabilize a projectile, it has to do with difficulty in getting things lined-up for accuracy.

Twist, connected to velocity; imparts a stabilizing spin in RPM. Stability is important for a LENGTH, not a weight, not a bearing surface.

People who tell you that a twist will stabilize a certain "Weight", either don't know what they are talking about, or are making a huge generality with a lot of ASSumptions.

Also note that rotational decay happens MUCH slower, than a velocity decay. So if you have a bullet on the lighter side of stable, farther down range the bullet will have essentially the same RPM, but much less velocity; thus resulting in more stability.
Between myself and a couple shooting friends, the 77gr SMK from a 9-twist will keep things pointed in the correct direction past 1,200 yards. But that bullet passes Trans-sonic with flawless survivability.

For an estimation(not an absolute) you can look-up lengths, and use this calc:

http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

Just click on the "Length" tab on the left, look-up the bullet. Then return to the original screen and plug in the numbers, along with your specifics.
Here is your RPM math lesson for the day:
MV * 720 / Twist = RPM