It may interest you to know that a Def or Sp.Def IV of 30 will give the same Def or Sp.Def stat as a 31 IV at level 50. This goes for any stat where you are giving it 0 EVs. So it would be worth testing some of the 5 IV ones, as this could more than double your chances of getting perfect stats.
For some Pokémon you can get away with even lower IVs, for example 28 Sp.Def on a Naive Greninja is the same as 31.
To test this, go in the Showdown teambuilder and set the level to 50, then fiddle around with the IVs and watch the stats change. If you're using a 252 / 252 / 6 spread, every stat you're giving EVs to needs have a 31 IV, uninvested stats can use 30. If you need to use a 30 IV for Hidden Power, use 248 EVs instead of 252.
Now that I've finished my complex explanation, I can offer a Big Nugget for a 31/31/x/31/31/31 or 31/31/31/31/x/31 one.