I made two rope dart "heads": one's a practice head, and the other made from a railroad spike.
(The practice one's a 2"x6" duct-tape reinforced tube/bag filled with rice, and it's held up VERY well.)
I used to practice quite a bit for a couple months back in 2010.
Honestly I'm no longer really fond of "exotic" weapons/martial arts, since I got tired of the whole "3x the training of more contemporary weapons/martial arts to reach proficiency" thing that usually comes along with it. :p
The sling is the only exception to that "no exotic/inefficient/'soft' weapon" rule thus far, probably since being way outside of mélee range is a little more forgiving of boo-boos.
These days I stick with more efficient weapons, like longsword, dagger, spear, and sword&buckler.
Keep in mind that I'm not bashing other views on this--SOMEONE has to keep the tradition/s alive, after all.