OK so I'm getting the spread of 188 HP / 196 Spe / 126 atk to be the best atm, unfortunately Cloyster can never get past p. def Giratina-a in one hit so the idea is to run enough for sp def tina fey, throw enough speed for timid scarf kia (use jolly on Cloyster btw) and then throw the rest in HP. Its physical bulk is "ok" now I guess. To give an example, Exkiller will have trouble 3HKOing this if Sr support isn't provided and your running White Herb.
Sorry for the extremely late response also, I am terrible at these things :(.