eh I would say that is probobably is accurate but hey what dio I know?
Hey, have a little confidence. Actually, you only need 252 instead of 255. The extra 6 can go into HP probably...
They should have 512 EV's(divisible by 4 evenly)
Oh and for the nature it is your choice it just depends if you want it to hit hard and get hit first or if you want to get out of the gate quick and hit something with less power!