i have a double shackle setup on my truck with 63s, and i havent ever had problems with them unloading. in my limited experience, they only seem to unload if you tighten the center bolt too much. my advice is get some lock nuts on there and make sure you dont overtighten them. heres a pic of mine.
![](http://i1107.photobucket.com/albums/h392/Creationer425/IMAG0320.jpg)