Adding New Bones to the Character Skeleton.nif and .hkx

(I'm not sure this really fits into any particular forum, so I picked Skyrim General Chat.  If there's something more specific for general modding please move this there.)

I'm looking for any information I can find on adding new bones, in particular new nodes for weapons, on the character skeleton.  Ehamloptiran helped me a great deal in learning some of what this might require, but ultimately my ventures into this were fruitless (supposedly Eham had successfully done it before, but at the time couldn't remember anything beyond the steps he taught me).

So if anyone might have any useful links, or tutorials (I have yet to find a relevant one) on the subject of behavior editing to add new weapon nodes, I would be very appreciative if you would post them.

Some background on what exactly I'm trying to accomplish:  My intention with this is to move Greatswords from the back to the hip, as a step toward Longswords (which I will hopefully be able to implement in the same way as spears will be in Skywind eventually).  To accomplish this the last time I worked on my little project I tried just about every trick I could find on modding forums and Youtube, though my first attempt was simply copy-pasting WeaponSword and renaming the copy to WeaponLongsword, and then changing the NiStringExtraData of all the Greatswords from WeaponBack to the new WeaponLongsword.  However, while the changed the position of Greatswords, they would remain on the hip and not animate with the player.  Eventually after trying every other method I thought might work, Eham pointed me toward behaviors, namely the skeleton.hkx, though my attempt at behavior editing was ultimately failure, resulting is the Greatsword meshes not appearing at all.  Despite this I think behaviors might be the way to go with this, as from what I could reverse engineer from mods that put staves or shields on the back, they seemed to be using the exact same methods I was, though with success.
Something that would also be a great help would be information on changing a weapon's NiStringExtraData node value to that of an already existing node, without having to change the weapon type in CK to match that node (as currently weapons on nodes that don't match their animation type in CK don't animate, and I have no doubt this was the problem with simply adding a new bone in the skeleton.nif).