1) really easy in pitch, impossible in yaw
2) Yes, each time you strap it in, you have to reposition it, but it's so easy to do that this doesn't matter
3) IF you put the light in the lockblock right at the light's center of gravity, it'll stay put over all but the biggest bumps. Again, if it does slip, you just pull it back where it belongs. Also, if it's slipping one way persistently over time, you have the light in the wrong place.