How to modify bones?(Not scale)

[falconcool]

Hi,Sorry this my be a numb question,Is there any way to modify skeleton.nif already?

I tried using Nifskope to scale some of them,but the result is bad,,character's hair float above the character's head,even i changed the C/K's race skeleton into my modified one.

And,,plz tell me what's skeleton.hkx located at animation.bsa "meshes/actors/character/" is used for? I used hkxcmd to convert it into xml format,There is no animation insde this file,can't tell it's purpose yet.Should i modify this data to pair with skeleton.nif together?

I've tried to to rig my new mesh into vanilla's skeleton for 6 times,,it's size just doesn't fit well,,really need help.

Thanks in advance:)