[Bf-animsys] Best practice for "how to setup Bone rolls" ?

[Gaia]

Hi;

Over the last few days i tried to understand why the bone rolls for a 
given Armature have been chosen as they are. I was looking for some sort 
of "best practice for Bone roll"  in the Blender wiki or at 
blenderartists.org. I also looked at Blender's

     Armature -> Bone Roll -> Recalculate Bone Roll

and tried to make sense out of what is calculated there.

Since i could not find any clear how todo descriptions, i just collected 
what i found into a list of rules of thumb as follows. (And i do not 
know for sure if the rules make sense after all, they sound somewhat 
reasonable though)

- Determine the main rotation axis for each bone and consistently align 
the bone roll (either X or Z) to this axis
- For horizontal bones match Bone-Roll-Z with global-Z, and for vertical 
bones match Bone-Roll-X with global-X
- For all bones ensure that bone roll Z is in the same plane (i am not 
at all sure about this in particular)
- Use Bone Roll X for up/down movements, like fingers up/down (when 
looked from the side)
- Use Bone Roll Z for sideway movements, like finger left/right (when 
looked from above)

Now i'd like to verify that these finds make sense. And then add a "Bone 
roll best practice" chapter somewhere below

     http://wiki.blender.org/index.php/Doc:2.6/Manual/Rigging

However it would be nice to get some feedback and advise from a "rigging 
specialist", even a few lines of "raw documentation" that go beyond "I 
believe its so and so..." would be very helpful.

cheers,
Gaia