I need some help/pointers with gore caps for custom armor.

[BurgermanJones]

I've made a few NIF-bashed armors for a mod I'm currently working on, and they work well enough except for the gore caps, which don't line up with where the limbs actually sever (arms should sever in the middle of bicep, but the whole arm falls off). I've tried parting the mesh in certain ways, moving the caps themselves, and other methods as well, but I just can't seem to get it to work.

I'd appreciate any tips on how to best fix this, and would especially appreciate any offers to help, as I am very much a beginner with Blender.