i am looking at this kit

and i i am wondering if these will be ok for a slash 2wd for racing. i have heard of the shafts popping out of the cups and i am wondering if i am gonna have this problem. also i know it uses 2 set screws to hold them onto the output drives. i have heard of a erevo pin would fit through the kit so one pin holds the cup on. cause i hate the idea of 2 set screws holding the cup on. or is locktite just fine to hold the cup on. also does anybody know where to go to find replacement cups? cause i want to have a couple of spares just incase.