Yes, you're right, structures parented to structures is better. Just tested it out with the base of the tail structure parented to the hips structure and it's working just fine.
I'm not sure what was happening yesterday. I think initially, I had the "curve" setting on, and some animation on the controller before parenting the tail structure to anything, and when I parented the tail structure to another layer, it made the curve bend out of shape - I realized this morning that that goes away once you cycle through the animation once - but I thought it was a problem, so then I tried some other versions with different parenting and it seemed that whenever I parented the tail structure the FK seemed to stop working, but it might have been lack of keyframes at that point.
So I think with all the versions I just got confused.
If I parent the tail structure before adding "curve" or animation there's no change in the shape of the tail. And everything's working just fine.
Again, sorry for the false alarm. Everything's working like a charm!
