this is how i understand gaia explaining it to me...

the Default Shape for an avatar (make a new shape, do not touch anything) is not re-creatable, because somehow some of the values have decimal point settings, where the sliders only work with integers.

there is also a Neutral Shape, that animesh uses -- possibly the shape of the original rig without any sliders applied whatsoever. and THIS can't be reproduced as an in-world shape... because reasons?

the upshot is this:

the head, upper body and limbs of an avatar mesh don't match an animesh mesh, or vice versa. therefore, some meshes that look good as avatars are messed up when converted to animesh, or vice versa.

this is literally my biggest headache when trying to create rigged meshes for second life.

the only current solution is to upload the rig with joint positions, skin weight, AND 'lock joint positions' selected. this will ensure the rig retains its correct shape, BUT it also means that No Shape Sliders will work on it at all.

sure, the human head sliders probably won't work right on my animal head. but the users could at least change the head SIZE of the whole thing? it's not a very good compromise.

How To Fix:

1: one thing that's been asked for is to be able to apply shapes to animesh. then, if the Default Shape could be put onto the animesh, it would match its avatar counterpart. (i don't know how an animesh object would read an inventory body shape, but that's not my department.)

2: create through XML voodoo or what-have-you, a library shape named Neutral Shape, and have it match the animesh skeleton. then avatars could wear it, and they'd match the animesh rig.