I don’t know why it took me so long to realize this, but i just noticed you can set RVKs not only for lattices and meshes, but for curves as well. I got some really cool slinky kind of movement while fooling with it. sigh just thought I’d put this out there in case anyone else is unaware of this. 
happens to us all, and in fact that was not something I knew, so I learned something new today too! 